Last week the certificate for mail.boston.redhat.com expired. Every since then when I try to use evolution a dialog pops up that says """ Error while Scanning folders in "IMAP server mail.boston.redhat.com". Server unexpectedly disconnected: Input/output error """ I tried moving my .evolution folder out of the way and doing gconftool-2 --recursive-unset /apps/evolution but after resetting up my account it still happens. Thunderbird works okay. Note, I don't know if the certificate expiry is related or coincidence.
Are you seeing any relevant-looking output on the terminal?
Just: (evolution:3304): evolution-mail-WARNING **: Error occurred while existing dialogue active: Server unexpectedly disconnected: Input/output error
rpm -q evolution revealed it wasn't installed... My system was hosed, reinstalling evolution fixed the problem.