I've now upgraded to 4.8, but am still having this problem.

Can anyone shed any light on this?

Performance settings are as follows:

Page State Persistance: Memory

Module Caching Method: Memory

Performance Setting: Heavy Caching

Authenticated Cacheability: ServerAndNoCache

Compression Setting: No Compression

Use Whitespace Filter: No

I've tried various differnt settings, but none seem to work.

By server side compression, do you mean just in DNN? In which case the answer is no.

I'm afriad that doesn't work.

I've changed the setting, restarted the app, and then restarted IIS to make sure, but still to no avail.

I'm getting rather frustrated and desperate with this.

I've tried disabling anti-virus, firewall, etc etc but still nothing works!

I have a component called Element-IT.PowUpload installed on one of the portals for a client for managing multiple uploads, and that works fine.