Actually, it's more than a problem, it doesn't work at all. When I click the "Calibrate" button, it doesn't do anything at all. If I move the axis, the sliders barely budge. I have a .joystick file in my home dir, not sure if Vendetta uses that. I have a Logitech Dual Action gamepad. Has anyone else had this problem?

I don't use a joystick myself, but I believe there are a lot of joystick related threads in the Linux forum you could check out in the mean time.

Just a few, and most are about sticks not being detected.
For me the calibrate button in Linux doesn't do anything either.

Well fleabait, I did a forum search and couldn't find anything related to joystick calibration not working at all on Linux, though I'll admit I didn't look past the first 50 results or so. It would be nice to go ahead and get an answer such as "it doesn't work," or "you have to do [this] to make it work" in one straightforward thread.

I could be wrong IIRC A1 once said that the calibration button doesn't work under linux.
Vendetta doesn't use libjsw so calibration tools that write to ~/.joystick won't work.
To calibrate your JS use jscal (a demo app that is usually shipped with the joystick driver) or anything that directly talks to the driver.

Well, using jscal doesn't make any difference.
The strange thing is, for my analog stick, jstest outputs values as a singed 16bit int (about -32000 to 32000 with center as 0) but the values in the VO config files look more like they are in a 32 bit unsinged int range...

yeah, it'd be nice if you could just take calibration data and shove it in the config.ini