Hi Andre,
I'm surely sorry you're having trouble. Bring it by my (home) machine shop and I'll make it right for you in a blink!
Lacking that (I'm a ways from you...), you have a number of options, any or all of which are likely to work.
1) I agree with Hamish; drill it out. It is possible the fasteners were cross-threaded in factory assembly. It happens. If you go this route, I would start from the backside. The best way is to size the bit so it is equal to the OD of the chainring bolt shaft. It doesn't take much, and should do the job. I would place a hex key in the bolt socket to stabilize it while you drill; hold it, else the whole assembly will spin uselessly. Pad the crankarm to avoid marring. Done with care, your arms will be unmarked and all you will need to replace is the chainring bolt/sleeve nut set, salvaging even the rings in as-new condition.
2) In the event you're dealing with galvanic corrosion (unlikely since you were able to turn the fasteners a couple turns), use a penetrating oil, solvent, or spray. My favorite is a co-polymer called PB Penetrating Catalyst (
http://www.blastercorporation.com/PB_Blaster.html ). It will work when others don't, particularly on Honda and BMW fasteners, which are unusually prone to galvanic corrosion in their 10th year or so. Liquid Wrench is another popular on my side of the pond, though doesn't work as well. Lacking those, you might try opening a fresh can or bottle of Coca-Cola (Dr. Pepper will work in a pinch) and pouring it on the fasteners while periodically tapping lightly on the fastener itself. The drinks are carbonated and contain traces of phosphoric acid (that's why they eat tooth enamel) and do a surprisingly good job at loosening stuck fasteners when more formal means are absent. You may be tempted to use ammonia as when removing a seized quill stem or seatpost, but it will damage the aluminum. So will lye.
3) Often, the chainring bolts fail to fully penetrate the sleeve nut, leaving a small flange that will take a blunt-flush screw/bolt extractor (often referred to as an "Easy Out"). This can be used to stabilize the sleeve nut while you go at the bolt from the front. If you've also managed to strip out the hex fitting, then another will work in the former socket. The extractor will often work even with a flange too small to grasp with Vise-Grips (mole grips).
If these methods don't do the job, give a shout and I'll dive a little deeper into my bag of tricks. I had to go the whole nine yards on an in-tank fuel pump replacement last winter. A whole tank of fuel (and the weight of it), and the line fittings had seized completely. What a mess. Got it loose with no damage, but it took a careful mix of thought, force, and patience.
Truly, best of luck Andre. Let us know how you come out...
Dan.
