I too had this error, and found many forums claiming the issue was with the BES my BlackBerry is attached too. However I knew my previous device (8703) had been attached to the same BES and was able to download files of this size without issue.
After working with Tech Support with RIM (via Tmobile) here is what worked for me:
-Options>Advanced Options (Wrench Icon)>Browser: Make default Browser 'Internet Browser'
-Load browser>browser options>Cache Operations: Clear all the Cache
There was a hit under the BB forums as well relating to BES operation. But I used the fix from this post and it worked for me! Somewhere along the line I changed the default browser to Blackberry instead of Internet... so my BES was not cranked down as tight as I thought...
As mentioned the reason you get that message is because of the setting on the BES server and a work around is to use the Internet Browser (or any other Web browser).
This works because instead of you are now accessing the internet directly through the current carrier you're connected to instead of it being "proxied" through your BES server.
What this means is that you are now accessing data outside of what your Blackberry Tariff and charged at the carriers rates. (If you're roaming you may be in for a nasty surprise!).
any suggestions