[propbeanie]

When you did the Uboat Missions add-on, did you allow the Steam installer put it in the "default" folder, which is usually "C:\Program Files (x86) \Steam \SteamApps \common \Silent Hunter Wolves of the Pacific"? You need to put it in a custom folder outside of any of the "C:\Program Files" folders. Something that you create yourself. If you have another hard drive, you can create a new Steam Library folder to put the install in. I use drive "F:\" and created a "Games" folder on my computer, so I've got "F:\Games \Steam \SteamApps \ common \" for my Steam game installs. Also, did you let it install the DirectX v9.0c and the Windows Media Codec again? You might have to do that. I am not certain of that, since I do not have a Steam SH4 install. Only SH3 (very similar) and SH5 (very strange)...

Beyond that, if you have any mods enabled in your original v1.3 install, the use of the Steam "verify" will put all the files back to their "default" value, which effectively renders any activated mod corrupt, and might result in a game that will not start. If that's what happened, let us know. There is a way around that situation, but can be a bit complex.