If
george@mytown.com forwards to
george@mydomain.local, then this isn't global forwarding? If POP Collector is set up to forward that way, then ALL mail will end up in the account specified (whoever it was sent to originally). Global mailbox will mean POP Collector reads the headers to determine the recipients, and if one is found from the given domain, it is sent to the relevant user.
The default send from is not an issue. This is only used if the sender cannot be read. While it is best to change it to something relevant to you, it would not affect delivery or operation at all.
It would be beneficial to upgrade to 1.4.2, as a lot of work was done for Win2k8 support. Back up settings first though (the file in the POP Collector folder) as they are in a new location in the latest version.