"invalid sharepoint site url" appears when adding a shrepoint site in environment "K2 Object Browser" then try to explore the newly added shrepoint server you can see it here https://skydrive.live.com/?cid=9d428082aae39704#cid=9D428082AAE39704&id=9D428082AAE39704%21374
I have K2 blackpearl KB1370 and Windows Server 2008 R2 Enterprise 64-bit (6.1, Build 7601) Service Pack 1 (7601.win7sp1_gdr.110622-1506)
I saw http://www.k2underground.com/forums/t/10213.aspx but the DisableLoopbackCheck is already set to 1 in windows 2008 R2 registery