We just found a problem with APEX, :REQUEST and Interactive Reports.
If you use REQUEST in the Conditional Display of a Region that contains an Interactive Report, the filter and other IR functionalities will hang. Probably because Interactive Reports uses the REQUEST variable...
See a demo here and try to create a filter, you will see that the IR hangs. (If you look at the URL you will see 123 in the REQUEST : http://apex.oracle.com/pls/apex/f?p=33429:1:1104406850817908:123::::)
The workaround is to add a computation that sets a page item depending on the REQUEST value and use that page item in the conditional display of the Interactive Report Region.
It does not work in APEX 4.0 also (for now) : http://tryapexnow.com/apex/f?p=686:1:3857853599891690:123::::