cannot connect with WEP on

[JohnC5456]

If I try to access the internet with WEP turned on airport returns an error and will not connect. With WEP off it will. I have made sure I am using the correct wep code. I have tried a reinstall of OS (clean restore to defaults)

Any advice appreciated (New to Macs)

Has connected before but loaned it out for a project, now won't.

Thanks