DTM Studio, when should I consider a client locked up?

After what amount of time (i.e. heartbeat missing for X minutes) should
I consider a machine running a set of tests “dead” or locked up?

I have a set of tests on Windows Vista which ends up doing this
occasionally, but I am always hesitant to reboot the machine, since
there are those “sleep tests” and I don’t know exactly when they can be
considered failed and when they can be considered successful.

Any insightful comments are appreciated.


// Oliver