Error zipping large numbers of files

When selecting multiple files in FileVista the Download As Zip and Add To Zip functions seem to fail or be intermittent.
 
I'm selecting approximately 400 files (totalling apx 700mb) in a folder, right-clicking, and selecting Download As Zip.  The site then does some processing for some time, before finally displaying an error
"There was a problem retrieving the XML data:
Internal Server Error (Error 500)"
 
Following this error a file appears in the FileVista folder, download-yyyymmddhhmmss.zip which is large but not as large as one would expect.  If you download the zip file it won't open, saying it's corrupt.
 
Selecting the same 400 files, right-clicking, and selecting Add To Zip, the same thing happens - the named zip file gets created, but corrupts before completing.
 
Having tried this process several times (apx 15) it did once work the successfully downloaded an in-tact zip file.
 
The same process works will a smaller number of files / less data.
 
When trying to zip two large [zip] files (both apx 300mb), I get the same error/corruption.

Can you please advise us how to avoid this error.

May have something to do with a timeout?

http://www.gleamtech.com/support/forums/showthread.asp?TID=3224

Yes, this seems to be timeout issue, please increase the execution timout in web.config: 

<httpRuntime executionTimeout="1000">

Thanks, that's done the trick. Simon

I'm running verion 4.0 and I do not see <httpRuntime executionTimeout="1000"> in the web.config. What section of the web.config should I add it to?
Thanks,
Shane.

You should add this setting under<system.web> section.