A lot of applications have started to use Helvetica as the default font

[motin]

After installing the Helvetica font, a lot of applications seem to have fallen in love with it... QT applications all are using it, and evince uses it or no font when displaying PDF's. Opera also seem to be using it randomly for many websites.

I'd rather not uninstall Helvetica, but it would be great if skype chats once again could be readable and PDF's be viewed without Adobe's PDF Reader etc.

Anybody now what's cooking here?

[TCSnyder]

You can change the fonts of different things in System-Preferences-Appearance. but i dont know if that will help if they change by themselves

[kerry_s]

After installing the Helvetica font, a lot of applications seem to have fallen in love with it... QT applications all are using it, and evince uses it or no font when displaying PDF's. Opera also seem to be using it randomly for many websites.

I'd rather not uninstall Helvetica, but it would be great if skype chats once again could be readable and PDF's be viewed without Adobe's PDF Reader etc.

Anybody now what's cooking here?

Helvetica is already installed by default, why would you have to install it?
it's a bitmap font that comes in xfonts-100dpi/xfonts-75dpi, it's the linux alternative to arial font in windows, i use it as my desktop font for it's speed and it not needing smoothing and hinting to work. (see pic)
check all your font preferences, to see where it's set and change it. if your using qt programs in gnome, you can use qt3-qtconfig or qt4-qtconfig to configure qt programs, depends on which qt your running, there in the repo's just look in synaptic.