New hard drive in my home PC = upgrade to/new install of Ubuntu 9.10 last night.
I set up tightvncserver and all worked fine from home when I tested it last night. Today from my Macbook at work, though, odd keyboard mapping prevented using a VNC session.
A little searching online reveals that tightvncserver is apparently built with an old version of XFree. Removing tightvncserver and using vnc4server instead solved the problem.