I've had this problem for a while - with both Safari 4 and 5.
I'm using the latest 1password 3. Very regularly 1password will be removed from Safari automatically meaning I have to go back into 1password preferences and add 1Password back into Safari, which gets very tedious - mostly on a daily basis.
Also, when 1password is installed Safari can then take up to 5 minutes to become active - it will sit there seemly hung.
In 1password I've tried:
* rebuilding data file
* clearing cache
None of which solves the issue.
I do not have any Safari addons such as Glims etc.
Firefox, meanwhile works fine.
Thanks in advance for help.