how do single quotes get around my email address on some PCs?

I have an application written in VB that generates emails. It's been working fine on over 100 PCs, but now I'm starting to get emails from users telling me that the emails my software generates ALWAYS come back. The reason is that somewhere along the way, something inserts quotes around the email address - so it does not look like [email protected] but '[email protected]' - and Outlook Express won't send the mail...

It happens on SOME Windows XP machines with Outlook Express 6.00

Any help or guesses would be greatly appreciated.
opicka:confused:

Check that it isn't your code inserting the 's.

It's not my code that inserts the quotes, the problem does not happen on 99% of machines. I can't even replicate the problem myself, that's why I have a hard time figuring out what's wrong...

Thank you for your suggestion,
opicka