Thanks for your bug report. The issues you mention have been fixed for the next version. $cb() will need heavy testing in the next beta.
Regarding the intermittent $cb() results: I was able to reproduce this. It is due to Windows or other applications locking the clipboard, a shared resource, using OpenClipBoard(), and preventing access. This prevents mIRC from using GetClipboardData() or SetClipboardData(). There are several discussions on stackoverflow about this and the only solution seems to be to make the application try to open the clipboard several times. I implemented this for both /clipboard and $cb() so that mIRC attempts to lock the clipboard up to ten times. Unfortunately this did not work reliably and only calling Sleep(10) in between each attempt, to give other applications time to release the clipboard, resolved the issue. This means that calling either /clipboard or $cb() can now take 100ms in total. Note that there is still the possibility that they could fail as the process depends entirely on how long another application locks the clipboard.
