[MacTUG] mac mini user with poor video

[Reg Leland]

i have a mac mini user whose external monitor display has gotten very 
distorted. very bright, hard to read, flaring around desktop icons etc.
i have tried to adjust various settings to no avail.
i created a test account and the video display is no problem. the problem 
appears to be restricted to the user account.
any ideas on a fix...thanks..reg.