Hi Trevor
The DejaVuSans.ttf file is in the Stellarium\data folder. There is a later version out now also you have not mentioned what version of stellarium, just latest. The latest release is 0.10.4 and this did have a problem with text flickering. It was fixed for the next release. Download and install this
patch. It will show as version 0.10.5
www.iceinspace.com.au/uploads/stellariumpatch.ZIP
and see if it is any better on the fonts.
Barry