Andrius, you may want to move this question to ArcGIS for Desktop Installation support since this space us for questions about Geonet itself. To move Moving Content
What operation system are you working on? Was 10.1 working without issues before you applied the sp, or is this a new install? If so, you might want to try Resetting your ArcGIS application profile and then trying the install again.
If new, and on win8, you may need to make sure Microsoft .net 3.5 client us installed, as talked about in the comment section on this post ArcGIS 10.1 and Windows 8 | ArcGIS Blog
and of course...did you try rebooting and and just restarting the install? (Always worth trying if you haven't already)
