The best thing to do in situation like yours would have been to restart the computer. Some program may lock up on one profile, and don't give up the hold so easily.
Now, I assume that you have two profiles, with different names. Generally, the original is called "default", and the new one has whatever name you gave it. You should be able to get the profile manager, and select the one you want
I generally, right click on the Shortcut, and select Properties. Then, I append the Target line with -p, with the keyboard space before the -, apply and ok.
Then when you click on the shortcut, NS8 should open with the profile manager. You select the desired profile, and it should work.
I suggest that you keep the new profile, just in case there is any problem, and instead of using the profile manager you can extend the Target line of the shortcut by having <one keyboard space>, and the name of the profile, so that the line would be: "C:\Program Files\Netscape\Netscape Browser\netscape.exe" -p default.
I don't know how well it work to select to open with that profile. Try this, for now.
UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8) Gecko/20051111 Firefox/1.5