Hi,
 
I'm pretty sure that the ferret faq has a bunch of info on what the
problem might be when an elderly ferret has a loss of coordination/use
of the rear legs, but I can tell you what my experience has been: My
girlfriend and I noticed Zeppo, a friend's 6.5 year old albino ferret,
wobbling when he was playing (his rear legs seemed to be not working
so well, in particular).  We took him to the vet, and they did a blood
glucose check which came out at 40(mg/dl?), which is low.  I don't
remember the other diagnostics, but it turned out that he had an
insulinoma, and he went on Prednisone and lots of hand-feedings until
my friend could afford the surgery to remove the tumor.  Now, a year
after the surgery, Zeppo is a happy, hoppy, healthy ferret (even if he
is getting pretty old).
 
I'll forward the relevant parts of the FAQ in private mail.
 
Dennis
[Posted in FML issue 1133]