Thanks Darius for helping out sofar.
Already contacted the CS Cart helpdesk.
Okay - this whole issue of ours was due to a password protected folder created in Cpanel under which the developers store was hosted on our server.
After removing the password protection and reinstalling the SSL certficate al was well again.
Please for related issues we had see also our other topic, upgrading our store
http://forum.cs-cart.com/topic/44919-2nd-upgrade-fails-to-start-stays-in-loop-v434-v435/#entry251402
Glad you resolved it.
We've gotten this before when files have been uploaded to a WAMP stack .. or someone has selected ascii in their FTP - certain files corrupt and this message is the result when you try to download upgrade packages.