It depends exactly what you mean by "freeze up", but there are a few people who have had a couple of different problems with the eforce. Go and look at
the Piranha discussion forum and do a search for "eforce" or "e-force" - you should find a few posts about it. Failing that, post a new message there, or get in touch with John from PMI.
Sorry, since I don't have one of these little monsters I can't give more specific answers.