Solution: More often than not, this problem is due to a configuration error with the dial-up networking connection set up in Windows NT. Specifically, it is set to connect using an encrypted password, which is not supported on a standard dial up connection with our server. To check this setting, please read the following steps:

1. Double click on "My Computer".
2. Double click the "Dial-Up Networking" icon 
3. You should see a window similar to the one shown in Figure 1 below. Click on the "More" button, and then click on "Edit entry and modem properties...", as is circled in red in Figure 1.
4. You should now see a window similar to Figure 2. Click on the "Security" tab across the top, and make sure that "Accept any authentication including clear text" is selected. This is circled in red in Figure 2.
5. Do these steps, and then you're done.

Figure 1: The Windows NT Dial-Up Networking Edit Menu

Figure 2: The Authentication and Encryption Policy Screen