The Best Practice Analyzer (BPA) for Small Business Server 2008 (SBS2008) reports 'An error occurred trying to access the web' when it tries to update.
If you click on the 'About the Best Practices Analyzer' link you might see an older update than Configuration File version: 18.104.22.168
[ We had an SBS 2008 server that blue screened and had to be restored using a SystemState backup and SFC system file check - somewhere along the way we ended up with an old configuation file version of 22.214.171.124. When run, this threw up an error about WSUS 3.0 needing SP1, when SP2 was actually installed. ]
You can manually update by copying a newer SBSBPA.CONFIG.XML file into the C:\Program Files (x86)\SBSBPA\en directory. You can find a copy here; sbsbpa.config.xml version 126.96.36.199