Hi my name is ***** ***** to Just Answer. I am reviewing your question and will reply ASAP.
Do you still need assistance with your issue? Please let me know and we can proceed.
Do you have a single user license or is it a multiple user license copy of CS3? I can't guarantee, and remote connection is just an optional extra, we don't need to do that.
CS3 will only work on one computer. You activate it with Adobe, and it is locked to the computer you activate it on. So you can't install on other computers unless it is a multi license version. The reason it doesn't accept the serial number is ***** likely because it is a single license version.
You're very welcome, have a great day.
By the way, I use Gimp on all of my Macs and it is free, so no license needed. It is not as polished as CS3 but does everything that CS3 does.