WindowsXP SP2 IE maintenance policy prob

Since applying SP2 to the machines on my school network, all machines are getting a userenv error with event id 1091 and description:

“The Group Policy client-side extension Internet Explorer Branding failed to log RSOP (Resultant Set of Policy) data. Please look for any errors reported earlier by that extension.”

As a result the IE maintenance policies are not being applied (eg proxy settings).

I have been unable to find a resolution of this issue, apart from removing SP2, which works, but I obviously would prefer not to have to do that.

Thanks for any help.