Ok, so not a bug per se, but I was surprised at the ease in which $decompress could be confused, resulting in mirc freezing indefinatly (and on one occasion bluescreening after end-tasking it):

Code:
//bset &test 1 120 156 11 201 72 | echo -a $decompress(&test,b)


(YMMV in reproducing the freeze, I only had to play around for a few minutes though)

Those characters themselves were just a string of gobbldeygook I pulled from a few compressed lines of "The Quick Brown Fox Jumps Over The Lazy Dog", I can't claim to understand why the freeze occurs or how to properly produce it.

I feel this impedes the use of decompress/compress for 'over the line' style tasks (link compression, on-the-fly dcc zipping etc.) where trust cannot be fully established. I hope this can be fixed as I feel this is one of the best features in the new mIRC.