Does the seminar class not work with MikTeX 2.9?

I have been using the "seminar" document class happily for years, but I've
recently reinstalled MikTeX (and Texmaker) and now my slides won't
compile... :-(  I get an error message suggesting that it doesn't know what
"\slideheading" means.  (Even though I've installed the "seminar" package
and it seems to contain all the files like "slidesec" and so on that I had
before.)  I don't want to switch to Beamer because I have hundreds of
slides already made up in the "seminar" format.  Any ideas?
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