Hmmm...I guess by now it's too late for this tip, but here it goes anway, right down and dirty:

First, close Maya, if it happens to be running.

Then you'll need to find a MEL script called 'performUVSnapshot.mel' (should be somewhere here: [Program Path Dir]\Alias\scripts\others) and copy it to your scripts folder (eg. my documents\maya6.0\scripts). Maya will give these scripts prioity over those found in Maya's install dir, so you can keep it for later use, just in case you have to reinstall Maya (beware!).

Now open it in textpad.

Look for these lines:

int $kPLEMaxX = 2048;
int $kPLEMaxY = 2048;

Simply change the 2048 to the your desired value (I set mine to 4096), save the script and restart Maya. Select your geometry, call the UV Snapshot window and set the resolution to your heart's content. Voila!


Easy enough.