Hi, I'm afraid, despite all the suggestions mentioned, that I can't reproduce this problem.
Can you pleae ensure you're able to reproduce this problem with fvwm2 built from master, and if necessary, supply the minimal fvwm2rc file which shows this problem? One thing to bear in mind, when functions are involved, they'll grab the XServer. I'm wondering if you're noticing this on a laptop specifically because of the ms timeouts on what FVWM considers a single click and a doubleclick? Kindly, Thomas