Brian,

IT says that nothing has changed recently on the server. Routine OSX updates would have been installed and we recently upgraded to 10.2. I cannot say for certain when this started (it's been a while since i ran R on the server), but several months ago it was working on 10.1. I dont know whether it was working immediately before the 10.2 install or not.

How would I investigate the X Virtual Frame Buffer? Are there other troubleshooting steps I should try?

For what it's worth, we've had a number of weird permissions issues. Postgres is set to use IDENT for local unix authentication. It was working for a while, then suddenly stopped working. This has still not been resolved. I worked around this by adding a -host switch for our postgres backup command, but that's not a very good solution.