When I tried to install the NAV 5.0 SP1 client I ran into an error 1935. This may happen on Vista and Windows 2008.
Error 1935; an error occurred during the installation of
assembly component {98CB24AD-52FB-DB5F-A01F-C8B3B9A1E18E}. HRESULT:0×800736CC.
The solution is simpler then it seems. You need to install Microsoft Visual C++ 20005 SP1 Redistributable pack. Remember if you are running on a 64 bit system you need to install both x86 and x64 package.