How long since you purchased Pro? Has it been more that six months? If so, you'll have to purchase it again.
Make sure you are using the e-mail address you used when you first purchased Pro. Also make sure you bought it from the official site and not one of the numerous scam sites that are out there:
Lime Wire » LimeWire Forums
Most importantly, make a backup copy of any program you purchase over the internet without a hard copy. Burn it to a disc or store it on another hdd.
If you have billing questions, send a PM to
limenathan.