If you experience sudden slowdowns for your terminal services users and in your research you see the dwwin.exe or dumprep.exe is hogging the processor, disable windows error reporting. In fact, I think it is best to disable this on all terminal servers (and even all machines), unless needed, through a GPO. See http://technet.microsoft.com/en-us/library/bb490841.aspx for ways to disable error reporting.
When error reporting is enabled, an application crash spawns a process that collects information to send to Microsoft and/or for internal use. This process can really slow down your machine and in a shared environment like terminal services can have devastating effects. Luckily, it is easy to disable.