Hi, thanks for the bug report! Unfortunately (as is the norm lol) "it works on my machine", I know that doesn't help you even a little bit.
There might be other plugin incompatibilities. Could you send me a list of stuff that's running on top of the proximity plugin? How big the the file you are playing (in kb)? In what context do you try to use the plugin command (via button triggered event? in a common event? etc)
I'll try to help as much as I can. If we can't make it work, I'll send you the full source for free and you can try on your own.