troubleshooting VTL puzzle.

There are several reasons as to why a bias circuit resistor could fail. Most likely, I'm guessing at this point without a schematic in front of me, it sounds as if one of your output tubes is pulling grid current. If the output tubes are old, this becomes even more likely. Depending on the resistor type, total failure or significant value drift can occur simply from thermal cycling (heating and cooling). Remember, most of the low wattage resistors used in audio cost less than 5 cents (in bulk, much less). I'd replace the resistor with similar wattage and type, and monitor the voltage drop across it with the same output tube in place. As long as the voltage drop is the same as the other bias/grid resistors, then chalk it up to a faulty resistor.
VTL used to sell a "white book" that had the basic circuit schematic that they used in almost of their amps. They were very straight forward as I seem to recall and should be quite easy to troubleshoot.
Good luck.

Look at what Jcbtubes has suggested and if that is not it, I have seen the adjustable pot cause some problems.
Check it is the same value end to end(compare to the other ones which are OK) that is along the conductive track - the two outer tags from memory. Also from memory they are 10K pots, so that is what you should get.

Also put you meter from the wiper to one end and check there are no sudden jumps in value. Compare with the good ones again.
This is what showed up as wrong in my amp.

New output tubes, new pots (I replaced all of them just in case) and a new resistor - still running well 6 years (and another set of output tubes) later.

ummm... that was a while ago:
jcbtubes was right.
there was a bad tube that actually is causing this 10Ohm resistor to bloe.
EveAnna Manley sais that this resistor is kind-of a fuse that prevents the bias circuit to blow.