This will be my third post to this forum this month seeking help. No replies to my previous posts on separate issues but I’m hoping someone can help me with this one. 
I’m trying to make basic changes to the default theme using the Theme Editor. For example, I’d like to turn rounded corners off so I clicked the slider to “off” and the loading spinner appeared over the center of my page. But nothing happens. The spinner doesn’t go away and the changes aren’t saved.
I’ve checked permissions on all my theme directories (all 777) so I don’t know what else it could be?
[attachment=7308:theme_editor.jpg]
Check the theme file permissions too and check your error logs.
The “spinner” is usually an ajax request that is waiting for a response. You can use firebug on the browser but as Stellar says, check the error_log for any php errors.
Note too that 777 may not be correct permissions for your server. Check with your host.
you should select a preset to save your setting. What I saw from the attached Image.
[quote name='StellarBytes' timestamp='1382738597' post='170399']
Check the theme file permissions too and check your error logs.
[/quote]
Is there a specific directory or file within the theme directory that could be causing this issue? And should all the files within the theme directory have the same permissions (whether it's 777 or 755 or something else) so I can at least do a recursive permission change (obviously there are a ton of files and directories in there, don't want to check them one by one).
Ok, here's where Firebug says the page is hanging:
[19:50:33.414] GET https://STOREDOMAIN/store/tb/index.php?dispatch=theme_editor.get_css&css_filename=standalone.css&&preset%5Bdata%5D%5Brounded_corners%5D=off&preset%5Bdata%5D%5Blinks%5D=%23ffffff&preset%5Bdata%5D%5Bmenu%5D=%23ff00ff&preset%5Bdata%5D%5Bmenu_links%5D=%23ffffff&preset%5Bdata%5D%5Bbase%5D=%23ffffff&preset%5Bdata%5D%5Bfont%5D=%23ffffff&preset%5Bdata%5D%5Bprimary_button%5D=%23ffffff&preset%5Bdata%5D%5Bsecondary_button%5D=%23ffffff&preset%5Bdata%5D%5Bsidebar%5D=%23ffffff&preset%5Bdata%5D%5Bprice%5D=%23ffffff&preset%5Bdata%5D%5Bdiscount_label%5D=%23ffffff&preset%5Bdata%5D%5Bin_stock%5D=%23ffffff&preset%5Bdata%5D%5Bout_of_stock%5D=%23ffffff&preset%5Bdata%5D%5Btop_panel_links%5D=%23ffffff&preset%5Bdata%5D%5Btop_panel_text%5D=%23ffffff&preset%5Bdata%5D%5Bfooter_text%5D=%23ffffff&preset%5Bdata%5D%5Bdecorative%5D=%23ffffff&preset%5Bdata%5D%5Bbody_font%5D=Arial%2CHelvetica%2Csans-serif&preset%5Bdata%5D%5Bbody_font_size%5D=&preset%5Bdata%5D%5Bbody_font_style%5D=normal&preset%5Bdata%5D%5Bbody_font_weight%5D=normal&preset%5Bdata%5D%5Bheadings_font%5D=Arial%2CHelvetica%2Csans-serif&preset%5Bdata%5D%5Bheadings_font_size%5D=&preset%5Bdata%5D%5Bheadings_font_decoration%5D=none&preset%5Bdata%5D%5Bheadings_font_style%5D=normal&preset%5Bdata%5D%5Bheadings_font_weight%5D=normal&preset%5Bdata%5D%5Blinks_font%5D=Arial%2CHelvetica%2Csans-serif&preset%5Bdata%5D%5Blinks_font_size%5D=&preset%5Bdata%5D%5Blinks_font_decoration%5D=none&preset%5Bdata%5D%5Blinks_font_style%5D=normal&preset%5Bdata%5D%5Blinks_font_weight%5D=normal&preset%5Bdata%5D%5Bprice_font%5D=Arial%2CHelvetica%2Csans-serif&preset%5Bdata%5D%5Bprice_font_size%5D=&preset%5Bdata%5D%5Bprice_font_decoration%5D=none&preset%5Bdata%5D%5Bprice_font_style%5D=normal&preset%5Bdata%5D%5Bprice_font_weight%5D=normal&preset%5Bdata%5D%5Bbuttons_font%5D=Arial%2CHelvetica%2Csans-serif&preset%5Bdata%5D%5Bbuttons_font_size%5D=&preset%5Bdata%5D%5Bbuttons_font_decoration%5D=none&preset%5Bdata%5D%5Bbuttons_font_style%5D=normal&preset%5Bdata%5D%5Bbuttons_font_weight%5D=normal&preset%5Bdata%5D%5Bgeneral_bg_color%5D=%2300ffff&preset%5Bdata%5D%5Bgeneral_bg_image%5D=transparent&preset%5Bdata%5D%5Bgeneral_bg_repeat%5D=repeat&preset%5Bdata%5D%5Bgeneral_bg_scroll%5D=scroll&preset%5Bdata%5D%5Btop_panel_bg_color%5D=%238e7cc3&preset%5Bdata%5D%5Btop_panel_bg_grad_stop%5D=%238e7cc3&preset%5Bdata%5D%5Bcopy%5D%5Bfull_width%5D%5Btop_panel_bg%5D=1&preset%5Bdata%5D%5Bcopy%5D%5Btransparent%5D%5Btop_panel_bg%5D=0&preset%5Bdata%5D%5Bheader_bg_color%5D=%23ffffff&preset%5Bdata%5D%5Bheader_bg_grad_stop%5D=%23ffffff&preset%5Bdata%5D%5Bcopy%5D%5Bfull_width%5D%5Bheader_bg%5D=1&preset%5Bdata%5D%5Bcopy%5D%5Btransparent%5D%5Bheader_bg%5D=0&preset%5Bdata%5D%5Bcontent_bg_color%5D=%23ffffff&preset%5Bdata%5D%5Bcopy%5D%5Bfull_width%5D%5Bcontent_bg%5D=1&preset%5Bdata%5D%5Bcopy%5D%5Btransparent%5D%5Bcontent_bg%5D=0&preset%5Bdata%5D%5Bfooter_bg_color%5D=%23ffffff&preset%5Bdata%5D%5Bfooter_bg_grad_stop%5D=%23ffffff&preset%5Bdata%5D%5Bcopy%5D%5Bfull_width%5D%5Bfooter_bg%5D=1&preset%5Bdata%5D%5Bcopy%5D%5Btransparent%5D%5Bfooter_bg%5D=0&x=0.5257906995749019 [HTTP/1.0 500 Internal Server Error 2487ms]
[color=#880000][font=arial, verdana, tahoma, sans-serif][HTTP/1.0 500 Internal Server Error 2487ms][/font][/color]
[color=#880000][font=arial, verdana, tahoma, sans-serif]Note: I replaced my actual domain with STOREDOMAIN in the message above.[/font][/color]
Check your HTTP/Apache logs to see why you're getting the 500 error.
Generally if you are running php in suPHP mode, then you want all files and directories owned by the cpanel user/group and directories to all by mode 755 and files to be 644 (you could run tighter, but this will work).
My guess is that your 500 error is being caused by directory permissions of 777 somewhere in the path.
I upgraded to 4.0.3 and it started working.
You can also try your luck… 
Hey did you upgrade to version 4.0.3 went smooth. when I click install button, the installation went smooth but the default theme location is changed to /basic (i created a separate file for my own theme) and the preset is with this – value .
when I try to change the front page shows the error.
can you say me what you did to upgrade?
This error again started.
I am not able to customize my preset Theam.
Any permanent solution ?
If the theme editor doesn't save changes,
you can edit the css files using FTP Software
/cs-cart/design/themes/responsive/styles/data
I wanted to edit the color of the 'menu', and my theme was 'Modern'
So Open Modern.less in the above directory
And find the original color and change it to another color of your choice,
Once you save this, the settings will change.
And your website after refreshing will change to the new color