If SharePoint is importing disabled profiles, you should change the profile import filter.
1. Go to Shared Services >User Profiles and properties
2. Click on Configure Profile Import
3. In the Source area, click on "View import connections"
4. Edit your Active Directory connection
6. In the "User filter" field, paste the following string: (&(objectCategory=person)(objectClass=user)( !(userAccountControl:1.2.840.113556.1.4.803:=2))), see image below:
7. Click OK.
Microsoft article: http://support.microsoft.com/kb/827754