Design Tools / Sql Server Mgt Tools Cause Login Fail

Login failed for user 'TOSHIBA-USERASPNET'

I know that the file persmission for the web application have to include aspnet, so i keep resetting the folder permission for aspnet in file manager, but the login failed keeps coming back every day or two

problem is after working with VS05 Pro, SQL Server Management Studio CTP, somehow the aspnet persmission get changed, use alot of sqldatasource wizards and often there is a conflict/hang between the datasource wizard and the need to have the mdf in a dettached state within VS server explorer,

not sure but the procedure to fix this seems to be to reboot, detach and re-attach the mdf in the Sql server Studio tool, re-apply the aspnet file permission on the web app folders (wonder should i be doing this in IIS instead), make sure the mdf within server explorer is detached, the it works

anyway, getting real tired of the resulting delays and design time derailment, clues greatly appreciated, thanks

 sometimes i can use View in Browser when in VS05 form view and i wont get the aspnet folder permission error and other times i do.

last thing, is it a bad idea to give aspnet full permission for the entire web applicaiton??