DLLHOST.EXE Confiscating processor time

Hello everyone,
I work in a k-12 school system.
We have an MS Exchange 5.5 server running on NT 4.0, which gets its outside access through a Web server, running IIS, on a Windows 2000 advanced server. It is a Dell server with 2GB of ram and a 2.8GHZ Xeon processor. At least once (to several) time(s) a day DLLHOST.EXE is found to be using 100% of the CPU. There are also 2 processes of dllhost running on this server (see attached). When the server is restarted it is fine for a while. Is this something anyone is familiar with?

Thanks
GP