OK had an absolute F%$£&*(^ nightmare with this game under Vista (Vista................what a bag of SHIT ! ).
Right then - start game and changing the brightness give the above prob, also it works when the slider is moved - yes, but NOT permatly !
Agrivating................ picture is like you have two pairs of sun glass's on....... Here's the fix and this worked for me, and not been to knowledgable withis game, downloaded, installed and could not play but after reading the knob heads in the forum who think they know what they are on about is a little agrivating. ok, waffiling now, result :-
Run in Windows XP compatibility mode.
1) Right click on the Tremulous application or shortcut.
2) Select properties from the menu.
3) Click the compatibility tab.
4) In the group Compatibility Mode, check the checkbox and select Windows XP (Service Pack 2) from the list.
5) Also check "Disable visual themes" and "Disable desktop composition" and "Disable display scaling on high DPI settings".
Second option is to set r_ignorehwgamma to 1 and r_gamma to 3.0 (mine was "seta r_gamma "1.093750")
Well that is a little of a lie ---- "seta r_gamma "1.093750" I changed to ""seta r_gamma "6.000000" and after running the game the "seta r_gamma" in the autogen.cfg was set be the game its self.
Anyways this worked for me....................................