We released AutoCAD and AutoCAD LT 2013 Service Pack 1 recently. Unfortunately a limited install crash issue was found in the original Service Pack 1 after release, so we recalled it. We sincerely apologize for the inconvenience.
There is a new AutoCAD and AutoCAD LT 2013 Service Pack 1.1 with the issue resolved and will install on any AutoCAD and AutoCAD LT 2013 with or without the original Service Pack 1 installed.
AutoCAD 2013 Service Pack 1.1
AutoCAD LT 2013 Service Pack 1.1
More from the AutoCAD Support blog “Without a Net”
The Return of SP1 for AutoCAD and AutoCAD LT 2013