Cascading List of Values Error

Wondering if anyone has come across this one before. I've created to cascading LOVs using hierachies and have both in the same query in a WebI report. I can select the parameters ok, but when I try to run the report I get the following error:

Database error: [Data Federator Driver][Server] Temporary View definition found several times (IES 10901) (WIS 10901)

I tried adding indexing to the objects but still got the error and googling has not yielded anything helpful.

Thanks

Mark