I've also had this problem, although I was using DOS/Win98 fdisk, so
this may not apply to you. It seems that because the logical partition
was non-DOS that fdisk couldn't cope with it and so says none exist,
although of course it seems to remember when some do when it comes to
deleting the extended partition. Have you tried the fdisk in Linux
(assuming that's not the one you're talking about). I'm not sure if you
can delete a Linux partition that is mounted (i.e. to boot the system
with), if you can't you might find you can make a couple of floppies to
boot linux and run fdisk from, probably the ones from the installation
set will do, or a rescue disk.
Stephen.
DISCLAIMER: Like M$ I don't know much about good operating systems,
however, unlike M$ I'm willing to try and learn how, so if the
information provided above is incorrect, please don't kill me.