NBG - Did you ever work out what was happening. We are getting a similar issue with users on 3 tier Deski when they don’t get it when straight Deski. (We are using 3 tier to get through firewalling from some sites).
We are BOXI R2 SP2.3 and the report is newly created in this environment.
I too have many threads in this forum about this error,but mostly it says like
when there is not enough memory this error happens and before opening the particular report we need to close all the tabs that are running.Just give a try.