If a SalesLogix 7.5.1 Web Client user is unable to access a particular type of page, (Account, Contact, or Opportunity pages for example) even when the SalesLogix login is performed at different workstations, and other users do not experience the same problem, it probably is due to some contaminated user settings in the VirtualFileSystem table. Use the below SQL script to delete expendable user settings. The deleted settings will be recreated when the user logs in and resets options, such as visible tabs. (Before running the script in the SalesLogix Admin, replace UserName with the actual SalesLogix user name.)
delete from virtualfilesystem where modifyuser = 'UserName' and itemname<>'UserName'
After executing the script, an IISRESET must be performed to remove a copy of the old settings from the IIS cache.