Just try

Delete From QSpace.dbo.Prod_XRef Where SSN = @SSN

a) i believe you need the From clause and b) if the SSN Column in your table is defined as Char(9) you shouldn't need to perform a Cast or Convert.

Also looking at the message, you may need to change some of the settings in your connection string. Are you performing this from an application of some description ? have you tried running the query from query analyzer?