Performance issues with COM component

We have developed a web based .NET application (.NET 1.1 using VB.NET and
ASP.NET). Part of this application calls a third party program using a COM
interface.

We have noticed that in certain situations, especially when the third party
application is performing lengthy or complex processing, the User Interface
to our appplication completely bogs down and performance slows to a crawl.
These COM processes are spawned as asynchronous server threads not related to
the UI so we are at a loss to explain this. In this particular case, the
server is extremely powerful (8 GB RAM and 8 processors) so there should be
enough hardware to handle the load.

We are trying to capture more information using the Performance Monitor but
are unsure as to what processes should be designated. Does any one know what
counters would be useful to include or whether there are other tools that can
help us isolate the problem?

TIA