Some users do have this problem also on my site (3.0 and 3.1)
I switched off vb35-Integration on 3.0 and all wents fine. Today, after upgrading vb35 to gold and RP from 3.0 to 3.1 i switched integration back on.
I tried posting with Opera, Firefox and IE (all version up2date).
I uploaded a testproduct and asked all users to review it.
All Users who had that problems are using IE.
I thought it has something to do with the WYSIWYG-Editor (als enabled ALL vb35-Intergartion-Options), but if i disable (only) the WYSIWYG-Editor and leave the other vb35-Option on, i only get a errormessage then showing a product. (If you need the exact errormessage, i will have to switch it back off).
You find my installation here: http://www.entertainment-foren.de/rp/