I use signals in an autoupdate routine. I download the new version, ask the user if he wants the new version, and if he does, I load it.

mIRC doesn't work well with this. The signal gets called twice, and I wasn't expecting it, so I had to recode it to handle the mIRC bug. It was very hard to find the problem, because mIRC reported a bwrite error (the binary variable disappeared before the second signal calling).

This is similar to this bug, except the other bug doesn't require a reload.

Notes: For some reason, if you call the signal yourself with /signal test, it doesn't cause the bug. If you have another signal handler that will handle test (on *:signal:*:) it might not cause the bug. mIRC 6.11 is affected by this bug.

Bare minimum example :
alias test .signal test
on *:signal:test:{ echo 4 -a Signal was run ! | if ($input(Wait ten seconds then click yes, y)) .reload -rs $+(", $script, ") }