More than half of the time, when I quit Lightroom 3 beta, I get a notice saying that "Adobe Photoshop Lightroom has encountered a problem and needs to close," and asking if I want to report this to Microsoft. Note that this occurs only AFTER I ask Lightroom to close, by typing Alt-F4, or mousing to File > Exit, or clicking the x close box on the main window. It doesn't happen all the time and I don't see any pattern (like it does this only if I've just exported files and doesn't do it if I didn't export anything). Still it's annoying and worrisome.
Windows XP SP3 on a Dell Latitude D820 with 4GB of physical RAM (3.25 effective).