Whenever I make an attempt to update to SP1 it will output the following error:

Error 1328. Error applying patch to file C:\Config.Msi\PTEBB.tmp. It has probably been updated by other means, and can no longer be modified by this patch. For more information contact your patch vendor.

Then, when I try to install SP2 it complains about SP1 not being installed.

Any ideas why this might be?
Thanks in advance.