Sync Problem

[knocx]

When user Changes his/her ftp password, (sometimes) IIS directory security password does not synchronize with the replacement, hence IIS asks for a network password when the website http is requested ,

when i overwrite the IIS directory security password with the ftp password it works (Does not asks network password)

Config ;

Plesk 7.5 Win Dual Xeon with
MSDNS
Serv-U 6.0
Merak 8.x


Anyone had the same ssue?

Thanks
knocx