For the last few days I’ve not been able to get steam running, it just sits at “Steam – Updating – 0%” and does nothing. It was allowing safe mode but after trying to reinstall it from the download it lost that too. One fix on the forums says to delete StreamUI.dll and try again, but that didn’t work.
In the end it turns out that Steam doesn’t like network bridges. Deleted the bridge and deleted my second network port and it went straight in. Finally!