BI exception with class "BIBaseRuntimeException"

Dear experts

We upgraded from NW 7.00 to NW 7.4.
After applying the newest delta patches for Java, and trying to test Bex functionality we are getting the following error:
"Caused by: java.lang.NoClassDefFoundError: com/sap/tc/ur/browser/BrowserDescriptor : cannot initialize class because prior initialization attempt failed"

The diagnostic tool displays a green status.
Both ABAP and Java are on NW 7.4 SP5.

Any ideas?

Cheers

Marian