This problem has gotten worse over about 2 months, so that now, everytime I open Mail and attempt to click on any one of my inbox messages that have already be delivered, the program quits, and I get the dreaded "application has unexpectedly quit" message box. Furthermore, any mailbox I attempt to click on the left column (sent, trash, etc) also yields the same results. Mail is essentially totally unusable. I'm running fully updated 10.4.9 on a Powerbook G4 and a stock copy of Mail with no plug-ins. I've been digging through Google for solutions, but most seem to be cases involving older versions of Mail with older versions of OS X. Doesn't seem like it would be applicable here. I've tried a few basics: restart, reinstall the 10.4.9 update, repair permissions, and check disk. Nothing has helped. I haven't gone as far as to remove my mail preferences file, because I'll loose all my mail messages. I have several years of 3 gmail accounts in mail. I absolutely can't loose those. I have several backups of the mail folder and the preferences file I could drop in, but only at last resort. Can anyone suggest another solution? Could a corrupt preferences file cause this issue? Is there anything else I can do to try and fix Mail, short of reinstalling OS X?