[Qgis-user] Reset GISDBASE for GRASS plugin

[Micha Silver]

How can I get out of this loop:
Starting QGIS I get this error:
terminate called after throwing an instance of 'QgsGrass::Exception'
  what():  G_getenv(): Variable GISDBASE not set

If I start with qgis --noplugins it opens, without GRASS, of course. But
there's no way now to reset the GISDBASE without the plugin. Catch 22...

I'm on Scientific Linux 6.1 with a self compiled version 1.7. Where can
I find QGIS settings for the GRASS plugin?

Thanks,
Micha