I logged into another user and ran a quick scan using avast and it said that some files could not be read. in the scan log the filename is
C:\Windows\assembly\NativeImages_v2.0.50727_32\System.Runtime.Seri#\a33b3b88fd575b703ba4212c677880ae\System.Runtime.Seriaization.ni.dll
Other users on the laptop are working ok