screensaver causes error "share does not exist on the server" to endless loop

I've been trying to learn to automate my home Mac environment with Applescript. I've had some success, but am running into seemingly inconsistent and troublesome errors. In order to diagnose the errors, I've broken the scripts down into their component parts and narrowed the most troublesome issue down to the Screen Saver. When I activate the current screen saver via a script, or if I access the Screen Saver control panel via the System Preferences, I get

I can click the "OK" button and it dismisses, sometimes for good, but most often it loops endlessly and my only option is to force a restart by holding down the power button. I've tried force quitting all open apps, and relaunching the finder and the error message/dialog box loop remains running.

Oddly, starting the Screen Saver with the Hot Corner does not seem to trigger the error.

To me this indicates that the issue isn't with my script, but that there's a problem with my Mac.

For what it's worth, I've also had issues with connecting to my Time Capsule backup which is the only drive on that server.

The machine is a MacBook 13-inch Late 2007 running OS 10.7.5.

Thoughts?