ME2 in general, PC and Xbox all have this issue, and I would bet even PS3. The two ways to get down are to reload a previous save and DON'T hit the point that got you there, or to try and find a way down or on to another are to get down by walking along the edge and hoping. The clipping glitch is kinda common and annoying, with some useful instances if you want to watch youtube ME2 glitches to find some "cheats" that let you use this issue for your gain. Personally just reload a save and continue on BUT DON'T SAVE AND RELOAD IN THAT AREA OTHERWISE YOU MAY HAVE TO RESTART GAME DEPENDING ON HOW MANY SAVES YOU HAVE.