Cant Open Old Orders

I just imported my database from 2.2.4 to 4.0.3 (multi-vendor). Everything seems to be ok except for the fact that I can't open most of the old 'completed' orders. I'm getting the message below



503 Service Unavailable



[color=#000000]The server is temporarily busy, try again later![/color]









I have no problem opening new 'completed' orders. Any idea?

[quote name='buging' timestamp='1390028412' post='175420']

I just imported my database from 2.2.4 to 4.0.3 (multi-vendor). Everything seems to be ok except for the fact that I can't open most of the old 'completed' orders. I'm getting the message below



503 Service Unavailable



[color=#000000]The server is temporarily busy, try again later![/color]









I have no problem opening new 'completed' orders. Any idea?

[/quote]



I forgot to mention that this happens when viewing the orders from the storefront and admin panel