permission issue with tempdb works fine in SQL2000 but not SQL2005

the following SQL works fine in SQL2000 but gets a permissions error when run on SQL2005:

IF not exists (SELECT * FROM tempdb.dbo.sysindexes WHERE NAME = 'PK_tblGuidContractMove')

BEGIN

IF @.DEBUG = 1 PRINT 'airsp_CopyContracts.PK_tblGuidContractMove'

EXECUTE('ALTER TABLE #tblGuidContractMove ALTER COLUMN guidSource GUID NOT NULL')

EXECUTE('ALTER TABLE #tblGuidContractMove ALTER COLUMN guidDestination GUID NOT NULL')

EXECUTE('ALTER TABLE #tblGuidContractMove ALTER COLUMN guidContractMove GUID NOT NULL')

EXECUTE('ALTER TABLE #tblGuidContractMove WITH NOCHECK ADD

CONSTRAINT [PK_tblGuidContractMove] PRIMARY KEY CLUSTERED

(

[guidSource],

[guidDestination],

[guidContractMove]

) ON [PRIMARY]')

END

The user permissions are set the same in both 2000 and 2005 can you please explain what changed and what are the minimum permissions need for the user to be able to make these changes to the temporary table which the user created.

Moving to Transact-SQL from SSIS.