FF and TB typing freezes and other problems

Problem 1: used my FF 3 and TB 2 for years without any problems on a 1G SD memory card and they take only 1/4 of capacity with 7 accounts. But for about a year now, I've had problems while typing - it freezes or moves in leaps and bounds (as it does now). Both TB and FF also freeze before moving to the next window. Compacting folders, renewing inboxes and other advice did not help.

About 2 months ago I cloned in TB the same gmail pop account in Imap to check spam box without going to webmail, they're now both functioning OK in TB.

Problem 2: at automatic downloading I noticed a flash of a message that did not appear anywhere (saw the name of potential sender). Checked Trash and webmail - not there. Read Disappearing Mail in Help - no leads.

Problem 3: also noticed some replies do not register as Sent (green arrow)with the original message, but do appear in Sent folder. I suspect some of my replies never reach the destination as I don't hear back from many addressees.

Any solutions?

Thanks