Screen goes to nonsense

[eldergeek]

I couldn't figure out how to search for this problem, much less describe it. At some point after I boot up all text on my screen turns to nonsense. Doesn't seem to matter how long the computer has been powered up. This morning it had been on for less than an hour when it happened. Yesterday it happened after about nine hours. Does seem to be getting worse though. At first I thought it had switched to a foreign language but, on closer inspection, this isn't any language I've ever seen or even imagined. As I've said, I can't describe it but I can show you a screenshot. I was using Thunderbird when it happened this morning but the same thing happens in Firefox. Here's the screenshot:

http://www.don-guitar.com/temp/snapshot1.png

The only way to fix it is with a reboot. Suggestions?

[eldergeek]

Hmm, either nobody's seen this or I've stumped everyone. That's not a good feeling I'll drop by again later.

[SecretCode]

I was using Thunderbird when it happened this morning but the same thing happens in Firefox.

Have you seen it happen in any other applications? These are both Mozilla applications and not native KDE/Qt. What about LibreOffice / OpenOffice? (Same applies)

It looks like the fonts, or font cache, that these apps are using has got corrupted. However, I'm not sure where KDE stores / caches fonts for GTK+ applications.

In System Settings > Application Appearance > GTK+ Appearance, what widget style do you have and what is the setting for fonts?

[eldergeek]

I haven't changed any of these settings so I assume they're the defaults. Widget style is Oxygen-gtk and beneath that the selected radio button is: Use my KDE fonts in GTK+ applications, Incidentally my machine has been on constantly since I last rebooted, just before making my initial post, and the problem hasn't recurred.