Guys, I was having the same problem so far (tried an installation this morning, got the error and came here), then I tried something different from direct installing.
After the download of the installer files (that went up to the media5.cab file), I actually extracted them into a temporary folder to try a forced execution (cause when you open the .cab files on Winrar they actually show up the .exes and all other stuff). Well, it went no good, almost every .exe returned strange errors, but the curious thing is that the UPDATERUSA executable ran and opened the patch window. BUT FROM THE OLD MEMENTO MORI CLIENT (with this "Rise of The Reaver" update, things should certainly change in the patcher, but it was all the same from the first time I've played Requiem, more than a year ago) O_O . So not only we have missing files, we probably have the wrong ones :/