One of the vinyl tracks in a Tamiya T-34 I bought recently was badly warped. Short of exchanging the kit for another one, how do I go about straightening these tracks? Any help would be appreciated! :-)

Try setting them up on the running gear, a lot of the warping should disappear. I've never hear of a method of taking the warp out of vinyl otherwise. This could be the event that pushes you to aftermarket tracks.

Merry Christmas to all
The method that I used is to turn on your hot water tap and then twisting the track in the opposite direction and leting the hot water run over it from a few seconds to a minute or two depending on how hot your water is. This is a trial and error, but it works. I do it to form around the sprockets to get a better look. Have a look on my web page and you will see that all the tracks are done this way.
http://gta.igs.net/~dangelor/page_01.htm
NOTE: If the water is to hot ( closer to the boilling point ) you will deform the tracks, experiment with with one that you do not want.
mech (:-)