Had same problem on Fedora 15 after upgrade to KDE 4.6.4. kdepim version 4.5.96.
Workaround was to launch Akonadi Console, select "Local Folders" resource, select configure/configure natively.
Error appeared indicating current folder did not exist, select new path: /home/<USER>/.kde/share/apps/kmail/mail/
Kontact/kmail now working again as normal.
Had same problem on Fedora 15 after upgrade to KDE 4.6.4. kdepim version 4.5.96.
Workaround was to launch Akonadi Console, select "Local Folders" resource, select configure/configure natively.
Error appeared indicating current folder did not exist, select new path: USER>/. kde/share/ apps/kmail/ mail/
/home/<
Kontact/kmail now working again as normal.