Updated my $\LaTeX$ packages last night and noticed that it removed the $\AmS-\LaTeX$ package as it was obsolete. Ran the Beamer project I’m working on and a few of the slides were broken; random text inserted on the Title Slide where commands had not been recognised, and some formulae spacing and layout issues elsewhere.

After a bit of searching I found that the package had been replaced by $\AmS~math$ and $\AmS~cls$. Used the package manager to install, but the first two CTAN mirrors I tried returned “unknown file length” errors. Got both packages at the third attempt, and all is now running fine again.