eM Client freezing every couple minutes

Hi,
I have been using eM Client for almost one year, without any serious issues.
A couple days ago I transfered my application to a new pc.
It was working fine…
Today I did 2 things:

  1. The app asked for activation, so I cliecked reactivation. It worked.
  2. I set the offline usage settings to download all the messages from google so I can use search in all of my e-mails.
    Only one account has attachment download, the rest only e-mail without attachment.

After this the application is freezing all the time…
I can use it 1-2 minute only…
The only way to close is ending the task in Task manager.

I tryed deactivating local download…no change.
I uninstalled it several times, tryed with backup-restore and clead account adding… no change.

The eM Client is basically unusable right now…

Thanks in advance for any ideas where to start looking for the problem!