Apparently Linksys has changed the underlying operating system of its very popular WRT54G wireless router. Versions 4 and previous used Linux, and quite the cottage industry sprung up improving on the original code (including, of all things, running the open source Asterisk PBX to give you a VOIP home telephone exchange).
Now, version 5 of the WRT54G is said no longer to run Linux. Aarrgh. Peter Rysavy found
the serial numbers for v4 begin with CDFA andVersion 4 also has a faster CPU and more flash RAM than previous versions, so version 4 is the way to go.
the serial numbers of v5 begin with CDFB
Of course, other wireless routers use the same Broadcom chipset which allows use of the Sveasoft and other mod code, so Linksys may see sales of an otherwise marvelous product drop, at least as far as the digerati are concerned.