Text Color Error Message

When some but not all people that are using IE 6.0 hit the "text Colour" button on the post window an error message appears that says -

                A Runtime Error Has Occurred
                Line:  10
                Error:  Permission Denied

However, when those same people come to this forum they get no such error message and the "text colour" button works just fine?  What is the problem with my server or forum application.  I'm using 7.7 and Windows 2000.  -thanks