So I noticed that my Spotlight application icons were corrupted (just like the screenshot) ... annoying! However, I have since noticed two important facts.
First, if On My Command were installed before OS X 10.5 / Leopard (meaning I installed it when I was running 10.4), I didn't have the corrupted icons in Spotlight. So my old Mac is fine, my new Mac has the problem.
And second, now that I've updated to 10.5.7, my Spotlight application icons aren't corrupted. So it was a problem, but now it's gone. Whew!
UPDATE July 2009: the corrupted icons are back on the same Mac (On My Command installed after Leopard/10.5). They seem to go away just after a Software Update to OS X, and then come back until all application icons are corrupted. *sigh*