Mail keeps asking for keychain password
After doing the recent apple software update (now 10.5.8, mail 3.6) mail keeps asking for keychain password on only 1 of my 2 email accounts (both from same provider). The mail can work easily in the background then randomly asks for password. I can either re-enter the password or check cancel, wait and then "take all accounts on-line" it will work without me having to put in the password again - so I know password is correct and stored in account preferences correctly.
So far I have checked :
There is no time out lock out on the keychain login.
I have deleted the saved email passwords from keychain and re-entered the data again when mail asks.
The same email addresses work fine on ipad and iphone with no log-in/password issues.
I can easily access email addresses via their websites.
I have tried varying periods for when to check for mail - 1 min, 5min, 1hr etc.
On other discussion groups there were references to APOP setup issues but I have checked this and it is not the issue.
All these things did not stop it.
Any help please it is driving me crackers?
MacBook Pro, Mac OS X (10.5.8), mail 3.6