Question: Can't interupt evaluation

Greetings I'm having some problems where Maple occasionally starts "Evaluating" and the "Interrupt the Current Operation" does nothing (it becomes grey after clicking it) and Ctrl-Break does not work either. The only "solution" I've found is the end the maple process (which is always thrashing the CPU) in task manager, but this is highly undesirable as it means I lose all the work I did since the last save. I'm using Maple 13 on windows 7 x64 and it is happening 10-20 times per day with various pieces of code. Most of the time the I can interrupt when I get fed up of waiting, but other times I can't, and it's quite annoying. Any advice much appreciated. Thanks LR
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