Hiya, sorry to hear about your plight. In order to use KPPP you need to login as root just to create an account =). You just need to set 5 main things - account name, login id, password, phone no. to dial, device, modem speed. Here are the detailed instructions:
Lets say the following are your details:
Service - VSNL
VSNL Connection no.(Ph.No) - 022-24404444
LoginId - firstname.lastname@example.org
Password - abcd1234
Start KPPP through KDE. Click K button -> Internet -> KPPP
Now you will be presented with a screen which will ask you "Connect to", "Username", "Password".
Click Configure. A new window will popup("KPP Configuration"). Click the new button and go through the manual setup. There enter the "Connection name" as VSNL or whatever you use and the phone no you need to dial to call the ISPs server("Use the add button"). That will configure your connection with your ISP and you will return to the KPPP Configuration dialog box.
Now you need to setup your device(modem) and the speed. Use device as /dev/modem. Thats it!
Click on OK and you will come back to the first dialog box of KPPP. There fill in your login name and password and say CONNECT. And you will be surfing the web in no time!
Now if you have any further queries please ask. Also, remember Linux is a very serious system with very few flaws. Unlike windows it wont mess *anything* up unless *you* issue incorrect commands as SU or ROOT.
You need not reinstall Redhat everytime you need to use your internet connection. There must be a logical explanation for whatever is happening. If your connection works for the first time then it *must* work the next time and the next and the time after that until you alter some configuration! Also the lock file is used to indicate that the modem is in use by KPPP to prevent other programs from using the modem at the sametime.
 I forgot to ask which modem you were using?