>>>>Have run into occasions where on some computers, comboboxes and dropdown lists don't function quite right. In particular if you use a mouse, you can click on the control, the list does appear, but clicking on an item in the list does not make a selection when you click on a list item (i.e. the list is dismissed w/o making a selection). On the other hand, if you use the keyboard you can indeed make a selection. Does anybody have an idea of what may be causing this issue ?
>....
>>Unfortunately I didn't get much of a chance to "play around" on the systems in question long enough to see if I could notice if the usual "tracking" behavior of the listbox was present (after clicking on listbox, the selection bar "follows" the mouse).
>
>You probably did check, but only omitted mentioning:
>rodent population identical physically ?
>As today they all have probably have USB tails, differences in drivers possible ?
>
>If you still possess a grandfather mouse without USB, try that -
>or a very simplistic one without anything added by the driver for gaming or similar
>next step would be to check MoBo to be identical, Windows version and patch level
>then deinstall existing USB mouse drivers: identify via device manager
>with setting to show disconnected or similar (german version here)
>if you have a PE boot install stick, might be interesting if that shows same fluctuation
>
>If you access prg/vcx outside exe, scan disks for older versions
>
>regards
>thomas

Indeed I do remember some of the weird problems that occur with some mouse drivers -- but that was waaaay back in the PC/MS-DOS days. Often if you tried to use "no-name" or "off-brand" mouse, the provided mouse driver TSR was often buggy (and in many cases, it was bloated with a large memory "footprint"). Fortunately in most cases the communication protocol used by the mouse they'd use was a clone of a known "brand-name" one, so you just needed to find the right "mainstream" mouse TSR.