If I resume from sleep, the only what to get IMAP access again (to my gmail accounts) is to restart KMail. Accessing a subscribed-to folder by clicking on it doesn't work, nor does checking email manually. Going offline and back online again doesn't work either.

Anyone have success by killing kio_imap4 and restarting it? I haven't tried this yet.

This is a known bug in kio_imap4 unfortunately I believe.

Killing it may correct the issue.

I notice this bug has persisted into KDE 4.4 which is quite unfortunate since it is, and ought to be considered, a severe bug. I've moved, hopefully temporarily, over to Thunderbird in the meantime, but I quite prefer KMail, without the bugs of course.

The bug has existed for very long time, since the KDE 3 era I believe. It should be solved in KDE 4.5 assuming KMail 2 ( which uses Akonadi ) is shipped.