Mysterious Typeface Change

'For some most mysterious reason, this isn't the blog I once knew'*. Unaccountably and apparently of its own accord, the Title, Headings and Body changed from a serif to a sans-serif typeface. At the moment the sidebar Text and Headings seem to have retained their original serif selves. Who knows how and/or why.

I've checked through the template file and can't find any reason. Adding in specifications for assorted serif faces doesn't seem to have made a difference. The template may need "upgrading", but that will mean it loses a lot of the customization I've spent so much time on. It will all need to be re-done. I don't feel up to spending that time, concentration & energy all over again at the moment.

UPDATE: Viewing this blog on other machines shows it still with the approved, preferred, desired, serif typeface. So I dunno. Am leaving it alone now in case I make it worse.

* Music, sung (not very good version, RealPlayer); lyricses