I had detached a SolarWinds database called NetPerfMon that consisted of three data (mdf) files and one log(ldf) file.
That might be the problem. Detaching a db in SQL 2005 and later versions changes the permissions on the file. So it might be a permissions issue trying to read the existing files.
For that reason and others, I suggest using "SET OFFLINE" instead of detaching whenever you can.
SQL DBA,SQL Server MVP(07, 08, 09) "It's a dog-eat-dog world, and I'm wearing Milk-Bone underwear." "Norm", on "Cheers". Also from "Cheers", from "Carla": "You need to know 3 things about Tortelli men: Tortelli men draw women like flies; Tortelli men treat women like flies; Tortelli men's brains are in their flies".