Just downloaded and installed the Lightroom 3.2 update. I noticed that, although I'd previously set LR3 to open in 64-bit mode, the update overwrote that and defaulted back to opening in 32-bit mode. I've unchecked the "Open in 32-bit" check box in Get Info and everything opens fine now. Not sure if this is normal for Adobe updates - I'm sure the PS CS5 12.0.1 update didn't do this - but I thought I'd post this in case anyone misses this. Or, indeed, if anyone finds that it doesn't overwrite their preferences.