Hello.

Today I was messing around with some gconf (mostly /desktop/gnome/font-rendering) settings, and as a result, the fonts in some applications are completely wrong.
I've changed all of them to different values but nothing helped me out. One thing that bothers me is that the value dpi was originally set to <no value> but now it won't change back and insists on being set as an integer value.

This is a sample of how it looks in NetBeans: http://img25.imageshack.us/img25/3735/screenshotdo.png

I am running Fedora 11 with Gnome 2.26.3.

Oh my, that really is tiny.
Well, I'm not exactly sure how to help you here because I don't use Gnome as my full-time desktop and haven't for a long time, but I do remember that sometimes problems related to theming and fonts outside of gnome were related to the gnome-settings-manager daemon not being run in the background, so I'd check that first.

I'm a bit hesitant to suggest this, and I can't promise it will work, but if you erase the gnome and gtk settings in your home directory, then the next time you login they should be automatically restored to default values. Please don't attempt this without first doing backups!

Also, you may want to be a bit more careful with Gconf next time, it can bite you in the rear end like the windows registry editor