The problem seems somehow to be associated with the particular laptop that I'm running my test scenario on. The laptop has VB6 installed and when I try and compile the dll on the laptop, it fails.
Therefore I have implemented my dll and ASP pages on a seperate client machine that does not have VB6 installed and everything works perfectly.
I assume there is something corrupt on my design laptop - perhaps an SDK issue. At the end of the day however, I'm just happy to get the damn thing working!!
For the record, my dll is called and it's classes instantiated from ASP pages running on a client machine acting as it's own ASP server. The dll uses the SQLMerge object to connect and merge with the central server machine either via network connection or using RASDIAL api calls and a RAS connection.