radius question

We've had several users on dialup complain that they cannnot connect 
from time to time.  All of their settings are correct and they appear to 
have a password typed in their password box.  Yet radius says the 
password is blank.  When you re-type the password it connects fine.   I 
was wondering if this is a windows issue, ras issue or radius issue. 
Has anyone else experienced this?

Loren