I also don't understand what you mean by a DEP error.
Im guessing DEP = Data Execution Prevention
This is intended to stop applications running code which the OS thinks is data, as might happen with a virus. XP defaults to enabling DEP only for "essential Windows programs and services only". I don't know if windows considers shell extensions essential...
The problem can be an indicator of a bad function pointer. When debugging the issue, it is worth asking Eric if he enabled DEP and also what CPUs it happens on (IIRC, DEP is only fully supported on certain hardware).
PS: Forgive me for chiming in here - I recently experienced a DEP problem (in front of a customer!) and the concept was new to me... only showing itself on Windows 2003 Server (which defaults to DEP for all applications) running on a Xeon CPU. That turned out to be a "feature" of Ada tasking implementation and adding an exception was the only fix.