I experience the same problems but haven't been able to find a definite way of reproducing it on every system. Even on my system, it seems to depend on the loaded scripts; the more and bigger the scripts are, the more NP pool jumps each time I open/close the Editor. I have tried creating huge fake scripts and loading them on an otherwise clean copy but I can never get the NP pool to rise as much as in my every-day copy. It seems the bug needs variety :P
Even on the test copy however, if I open/close the Editor enough times (more than 50 or so), NP pool increases enough to be noticeable in Task Manager.
I have ruled out the antivirus theory. I can't rule out things like 3rd-party drivers but I doubt it, as mirc is the only program on my system that consumes that much NP pool.
