Well, I am not sure, the default name for the server that you host is called (Your iDevices Name) (Phone/Touch), its mainly just a preference.
I understand that sometimes things go wrong, however if you redownload it and try it again, if you have SBSettings maybe a process is running for it and its not responding, try running it in Safe Mode, the WEP code is a preference just as making a WAP code on your WiFi Modem.
If you have another iDevice, another iPhone or iTouch, try connecting the iDevice to a server, if it is an iPhone it doesnt matter and try using MyWi on their. I know that if someone is connected to a WiFi with a sercurity code and you broadcast the wifi it becomes available through a backdoor.
This should help get rid of the problem
1. Delete the package: MyWi (CyDelete or manually in Cydia)
2. Go and make sure that you have the native tethering on your phone not Cydia/Rock installed settings, my iPhone 3G has tething natively with 3.1.2 Fireware.
3. Turn Tethering off,
4. Reboot Phone
5. Go to Settings > Reset > Reset Network Settings This will just remove all cookies, caches, and history, as well as reset your Network Connections
6. Then install MyWi
7. Turn Broadcasting on
8. Voila!
This is the basic fix settings for any network source in Cydia because if it messes with the Network Settings you need to reset them so that it reset with that add on. Tell me if this works.