lost mail box lock error msg

Dear all,

Thanks in advance,

We are using outlook express with linux mail server and i receive these
message frequetly.

Header download for the 'Sent Items' folder did not complete. Your IMAP
server has closed the connection. This may occur if you have left the
connection idle for too long. Account: '*****', Server:
'192.168.1.200', Protocol: IMAP, Server Response: 'Lost mailbox lock',
Port: 143, Secure(SSL): No, Error Number: 0x800CCCDD

Regards,
Balaji