Removing mineral deposits from circuitboards

So, here's a fun one: See the picture(s) here: http://yahozna.dyndns.org/scratch/gridcase/ This is in a Gridcase 3+ I picked up last week off eBay for what seemed at the time to be a pretty great price. Heard some stuff rattling around inside so I opened it up before doing anything else and what I seem to have is a few large mineral deposits on the main circuit board. It's pretty well localized,and aside from a completely dissolved drive support post and a few rusted screws there really isn't all that much rust(amazingly). And thankfully the corrosion that's present has almost entirely avoided any custom ASICs or other parts on board. Everything else in the system aside from the bad patches in the pictures is clean (although the whole thing smells like a dank basement, geeI wonder why) and the underside is almost corrosion free so there's a non-zero chance I could get this running again. Except I have no idea how to go about removing the buildup of... crud... on this thing. It's pretty solid, I've soaked it for a few minutes in water and chiseled at it (gently) with the tip of an xacto knife and I got some of it off that way but it's very slow goingand I'm afraid of removing what's left of whatever's underneath it before I can identify it. Any tips for removing this stuff? (Also, as an aside -- my mails to this list are clearly making it to the list, but I never see my own posts/responses anymore... any ideas?) Thanks, Josh