Had a previous one, which worked fine for years until it finally gave up the ghost, so I'm sure it isn't a power problem. This new one is only a few months old, so I don't want to think it's hardware related.
I know it can get a bit picky depending on whether you're running the X53 pro software, so I'll carry on playing about with it for the meantime.
I'll try disabling the lights, though.
[EDIT]
Ok, pretty sure it's a software problem. If I load the X52 software (no loaded profile) and select the "programming" tab, It works when on minimum throttle (in control panel/devices and printers). Close the X52 software and it stops altogether.
