We host several websites.  We utilize a web-farm environment.  Two front end web servers (IIS 6.0), a file server, and a SQL2005 databse.  We recently upgraded from version 040904 to 050402.  One of our websites is very slow when a user is logged in; however, performs well when not signed in.  This spawned me to look at the performance of all our web sites comparing when signed in to not signed in.  I found all our web sites are slower when signed in; however, one site is extremely slow when signed in.  Does anyone know what is happening behind the scenes regarding page loading when a user is signed in? 

Thanks for your input Sebastion.  I did review the performance of SQL server, database requests, etc.  The problem was found to be the number of skins the portal was using.  The one portal that was very slow has multiple sites that uses multiple skin packages.  By deleting the  extraneous skins the site speeded up to standard performance.  There must have been a logic change from version 4.9x to 5.2x since this issue didn't exist in version 4.9x...Dave