If I remember correctly, the topic was addressed by David a couple of month ago, still I'd like to bring it up again as reminder:
Whenever Pegasus stumbles upon an incorrect email-address (here: incorrect use of quotation marks, i.e. using single ones, not in pairs), Pegasus throws a parser error dialog and stops, waiting for a confirmation.
On and off spammers seem to bring such incorrect emails into circulation, just often enough to make ANY use of rules that parse the address a real nuisance.
How to resolve that problem is a matter of the parser source and/ or personal preference: some people suggested a timed error dialog that automatically closes after a couple of seconds if no user activity is taken, some suggested to not show any dialog at all (or optional by configuration) - personally I'd prefer it not to be shown and instead generating an error entry for the Pegasus system messages window - I believe the error dialog was for debugging purposes only anyway if I recall David's comment correctly.