I bought an Indigo (v1) second hand via eBay, and the only problem I experienced were two wobbly pot's (ie the spindles/controls that the knobs sit on).
Unfortunately the only way you can fix these is by dismantling the Virus completely, to get to the circuit boards so you can de-solder and replace the damaged pots with new ones. If you want pics of the process, take a look at the links in this post:
http://www.sunesha.nu/virusforum/vie...?p=25178#25178
In these circumstances I'd imagine you can send the Virus back to your nearest Access distributor/retailer for them to then send it off to be serviced or something, but I've sourced some new pots and am going to do the invasive surgery bit myself.
In short, you might like to ask if there are any wobbly pots before you buy.