When I (administrator) want to compose a new email, I get en error on one of the first lines of my screen:

Warning: strpos() [function.strpos]: Empty delimiter. in /[path to sugar]/modules/Emails/Email.php on line 192

Next to this, all my signatures (html) are messed up since I upgraded from 4.5.0h to 4.5.1 last week.

Anyone knows a fix, another threat dealing with this issue or knows of a submitted bug?