I still would like to recommend to you, uninstall winfax on one of your machines for testing purposes.
Agree with Katie, that is program maybe your troublemaker. Winfax is known to be a Memory Hog.
We have some older PC's and Winfax gave us plenty of troubles on them.
We are sending our faxes the old fashioned way with the fax machine.
I just don't believe it is the newer Version of Vectorworks as we would have heard of the Memory Leak Problem already before.
Note: Let us know how you are making out. Good or Bad.
Tks