You can't update because Windows fails to detect the amount of free space on the hidden SYSTEM Partition which contains the bootloader:
2015-03-28 20:02:47, Error CONX ConX::Compatibility::CSystemAbstraction::GetDiskFreeSpaceW: Failed to retrieve disk space info for [gle=0x00000003] 2015-03-28 20:02:47, Error CONX CFreeSystemPartitionDiskSpaceChecker failed. Failed to determine the free disk space on the system partition. . HRESULT = 0x80070003[gle=0x00000003] 2015-03-28 20:02:47, Error CONX ConX::Compatibility::CCompatibilityHost::SetScanResult: Compat scan from provider wsc:setup: failed. HRESULT = 0x80070003
Error 0x80070003
means that a path is not found:
C:\Users\André>err 0x80070003 # for hex 0x80070003 / decimal -2147024893 COR_E_DIRECTORYNOTFOUND corerror.h # The specified path couldn't be found. # as an HRESULT: Severity: FAILURE (1), FACILITY_WIN32 (0x7), Code 0x3 # for hex 0x3 / decimal 3 ERROR_PATH_NOT_FOUND winerror.h # The system cannot find the path specified. # 2 matches found for "0x80070003"
So it looks like Windows fails to find the system partition.