This occurs because SharePoint cache of the WFE server/s are out of sync with the data in the Config DB.
There is a good KB article describing how to flush the cache here although it describes the process for WS 2003 not 2008. There are a few 2008 tips but here are the paths/config steps you will need to remember:
WS 2008- MS SharePoint cache is found here: Drive:\ProgramData\Microsoft\SharePoint\Config\GUID
WS 2008- Show hidden files: Click the folder, Select Organise from top bar menu and then select Folder and Search options. Click the Views tab and select option to Show hidden files, folders and drives.
The rest is easy enough to follow from the article.