To find out if it's system wide or user specific, try this...
Open System Preferences>Accounts, unlock the lock, click on the little plus icon, make a new admin account, log out & into the new account.
Does it work in the new account?
Try to get the big 10.5.8 combo on to it so we can reapply it afterwards...
1058 Combo Update, 10.5.8...
Safe Boot from the HD, (holding Shift key down at bootup), run Disk Utility in Applications>Utilities, then highlight your drive, click on Repair Permissions, then move these files to the Desktop, then trash the originals since move only copies them...
Then move these to the Desktop if they exist...
/Users/YourUserName/Library/Preferences/ByHost/com.apple.networkConnect.<12 digit number>.plist
Thank yo BD Aqua.
I tried all of your suggestions but still have the same problem. I downloaded the 10.5.8 combo on another PC then copied to the Imac using a USB key. I tried to download the Update Installer which I beleive will allow me to install this as a standalone s I dont have the interne. I cant get the update started as the instaler wont allow me to select the drive where to install it. Message says " This volume does not need installer update."
Also, a number of the plists above did not exist on my mac.
Thanks again for your help, look forward to any new suggestions.