I just figured it out. We both use Caffeine (Caffeine) to keep our machines from locking. Our corporate IT policy has us locked out of adjusting autolock ourselves, so Caffeine provides a good workaround. For some reason, though, the default configuration causes the cursor problem described in this thread. Caffeine is simulating the key-up of F15 every 59 seconds and this is somehow causing the runaway cursor in Wavelab. I’ve checked the key commands for Wavelab and see nothing assigned to F15, so I don’t know why this is happening. Nonetheless, I changed it to use F24 instead and the problem seems solved.
My thanks to bob99 and PG for helping me through this frustrating experience. 