Integris G2 Time out issue on Upload

Has anybody encountered the problem within the Integris G2 system, upon the point where you upload the data file onto they system, it comes back with a standard MS 'Page cannot be displayed' page.
The network we run on uses proxy server settings and the proxy runs Squid. This issue only happens when I am going through the proxy, if I connect directly on an ADSL it has no issues.
What I really need to know is if this application has any known issues with it or with Squid.
Why should a proxy server cause issues as it is all going trough port 443. If any one has experienced this or similar problems, please get in touch, as I really need to get this sorted. If you need any more information please let me know.

Thanks