After years of flawless operation, my Mach 3 on Windows XP finally has come up with a problem I haven't been to find an answer to in the forum...

It started with random "Art Code 9991" warnings/crashes, which (I think!) was fixed by a reinstall of Mach3. After the re-install, everything seems to working except I can't get Mach to reset the "Limit Switch Triggered" message. Nothing has changed in the physical machine set-up. In ports and pins, I can set the "Active Hi/Lo" to turn off the limit/home switch indicator lights in the "Diagnostics" screen, but this still does not allow me to Reset successfully. However, if I disable the switches in the "Post and Pins/Inputs", all axes work fine.

The "Auto Limit Switch" toggle on the "Settings" page makes no difference.

Any thoughts on how get my Limit Switches functional again??

Well, the problem turned out to a corrupted plug-in for the breakout board. Reinstalling the plugin (downloaded from the Artsoft site) solved the problem.

I suppose the lesson here is that a plugin that appears to be working correctly may still be causing problems in other parts of the system...