Error 'USBDeviceOpen failed' only with my user account when using PowerMate USB Controller. OK with fresh account
This sounds like something is broken with the device node for the usb device. You an compare the settings with something like this:


figure out what the device node is. The last step will output the device name following a > (and some other junk you can ignore.) You'll need that device name in step 2. It would be best to do this test on the temp user that works, just after a fresh reboot.

ls -1 /dev/ &gt; /tmp/before  (note, that's "dash one")
plug the device in
ls -1 /dev/ &gt; /tmp/after
diff /tmp/before /tmp/after

compare the device permissions between the two.

login as yourself
ls -el /dev/devicename &gt; /tmp/broken  (note, that's "dash e ell" this time)
login as the temp user
ls -el /dev/devicename &gt; /tmp/working



This last bit will create two files that look something like this:

crw-rw-rw-  1 root    wheel      11,   1 Mar 26 16:20 cu.Bluetooth-PDA-Sync

The first bit (crw-rw-rw-) is a textual representation of the mode bits... it's possible a difference there is the cause.

The next bit that might be the problem is the user (root) and group (wheel), either of which could be causing the problem.

I'm assuming it's being dynamically created (incorrectly) when the device is inserted. Another possibility is that the device node is persistent, but wrong. If both of those files MATCH, then show us what they are and we can probably figure out what the device should be set to.