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?

Update -

I thought that the Screen Saver might have been trying to call up images from a drive that used to be connected to the Airport Extreme but that is no longer there. I reset the Screen Saver control panel to one of the built in Screen Savers (after many tries at dismissing the irksome dialog box) and I deleted my user defined Screen Savers. This did not resolve or change the issue in any way. I've tried the same AppleScript on two other Macs without incident. Both of these other Macs are running 10.9.5 though, so that may or may not indicate anything.

Is there a way to re-install just the Screen Saver, or should I try to re-install the entire OS? Is there something else I should try?

Thanks!

Update 2

Well, re-installing the OS did not resolve the issue. I tried deleting the preferences plist from both the user library folder and the library folder at the top level of the hard drive. This didn't resolve it either. Perhaps it's an issue with the Airport Extreme, though I can't imagine why the Screen Saver in a re-installed OS would need to access the Airport Extreme. I'm really stumped here and beginning to wonder if I'm going to have to pay for more expert help. Thoughts?