Nightly build consists of an update of which two files are important, i.e. bsplayer.exe and bsrendv2.dll (these files always come in a pair).
Both these files should (of course with BSPlayer inactive!) be copied into the existing BSPlayer's installation folder (of build 808) substituting the build 808 versions of both files.
Did you do that (because I didn't have any problem whatsoever)?