I've just installed SBS 2011 and every 30 minutes this is logged (note: it's a swedish server, this is my translation, might not be phrased identically on english systems):
Logname: Application Source: Microsoft-SharePoint Products-SharePoint Foundation Date: 2011-04-04 10:00:00 Event-ID: 6398 Category: Timer Level: Critical Keyword: User: DOMAIN\spfarm Computer: SERVER.domain.local Description: An exception occured for runtime of jobdefinition Microsoft.SharePoint.Administration.SPUsageImportJobDefinition (ID 1abcd25a-5d73-49df-a757-c440b10364a3). More information below. Access to path SERVER-20110402-1559a.usage denied.
There are plenty of google results for the same event id but different error ("access denied to Program files\Common files\Microsoft shared\Web server extensions\14\LOGS", had that error, but fixed it following the instructions given on the web), but I cannot find any reference at all to this error.