Almost three weeks ago Autodesk released Service Pack 1 for AutoCAD 2013 and AutoCAD LT 2013. Within a couple days of its release the service packs were removed from autodesk.com while the AutoCAD team worked on resolving a newly-discovered fatal crashing error.
The service packs have been re-released (now as Service Pack 1.1) and the 32-bit and 64-bit versions of new update can be found at the following links:
This service pack is only for AutoCAD and AutoCAD LT (with or without SP1) and cannot be applied to vertical products that are based on AutoCAD 2013. If you managed to download and apply SP1 before it was removed, you can just apply SP1.1 on top of it. Uninstall of SP1 is not necessary or required.
Before installing Service Pack 1, I strongly recommend you review the associated readme file for installation instructions and details about the primary issues that are resolved by the service pack.