BlackBerry :: Update Settings For Gmail Account?

My blackberry (9700 Bold OS6) stopped receiving emails from one of my gmail accounts. Sending a message as following:Your gmail email messages are not being delivered to your BlackBerry® device. To receive your email messages, turn on the IMAP setting for All Mail in your murat account. After you turn on the IMAP setting for All Mail, you must validate your account on your BlackBerry device. 1. Click the Setup folder (if available), then click the Email Settings or Setup Internet Email* icon. 2. Click Email Accounts. 3. Validate your murat email account. The other email accounts on your BlackBerry device are not affected.

Problem is that the IMAP setttings for this account is ok. I also have another gmail account with the same settings and that is functioning very well. I also have Mail receiving programs on my computer which are receiving well all the mail via IMAP settings. So the problem is not the a settings problem but a blackberry's receiving problem.I tried validate the email address by writing my password, it validates but immediatly I receive a new message same as above. I also tried:

- cancelling and re-adding the gmail account (via internet site and also via phone)
- changing the password an retry validating
- cancelling service books
- formatting the blackberry and reinstallling the software

but none of these methods worked, everytime I received the same error message, whatever I tried to do.I called my operator, he couldn't resolve neither the problem, I even gave him my gmail account password to him so he can validate it in their servers, or so he can check my gmail settings, but everything looks normal.