I've just had a similar problem whereby the job would fail after it had copied the table structures. 

I eventually solved it by changing the options on the copy objects task to not...

Also, be aware of any packages that run as scheduled jobs.

DTSRUN ID change!!

I had a similar problem a while ago and came up with this for a solution.  Probably not the correct way of doing it but it worked for me.

You could also try using the sp_MSforeachtable sproc.  It might be a bit quicker.

EXEC sp_MSforeachtable @command1 = 'revoke select, update, delete, insert on ?...