Workspace Continues Running After Exit

[gr8dane]

I recently upgraded from TP 4.7.3 to TP 5.4.2 and at the same time started using workspaces for the first time. When I exit a workspace, TP appears to close properly, but my computer immediately slows almost to a complete stop. Upon investigation, I discovered that Task Manager shows TP still running until I shut down my computer (seven hours later, last night), at which time I get an error message indicating that the workspace is "not responding" and asking me to "end program."

I'm on an XP laptop (which is where the TWS file is) and editing files located on an XP desktop. What could be causing this?