Doing some quick googling, it looks like most reported cases of ADEM after rabies vaccination were from the older Semple vaccine, which used brain tissue. Supposedly, the human diploid cell version eliminated this concern, but it still looks possible:
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T1B-49M0VBP-5D&_user=75682&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000006078&_version=1&_urlVersion=0&_userid=75682&md5=465da174c6757154bce57d5d8c93b7d5
(Again, sorry about the format of the link; you'll have to do some cutting and pasting into the browser.)
You could well have ADEM (acute disseminated encephalomyelitis) brought on by the vaccination, and not MS. Since ADEM is usually characterized by only one episode and is self-limiting, I think it is almost synonymous with CIS. And it can be caused by infection or some vaccines.
http://www.adem.org/
http://books.google.com/books?id=t_qq-1E-lFsC&pg=PA47&lpg=PA47&dq=adem+vaccinations&source=bl&ots=za-bFUBzqB&sig=uf6OXeA5EXJufrOimV4uaBjeapw&hl=en&ei=lyuxStXzCN-x8Qa7vrzCDg&sa=X&oi=book_result&ct=result&resnum=8#v=onepage&q=adem%20vaccinations&f=false
(sorry about the length of the 2nd link).
I have never heard of vaccines causing MS. This theory gets floated around every few months, along with aspartame causing MS.
Why were you given a rabies vaccine?
Since no one really knows what causes MS it is hard to say. It is believed three factors are responsible for MS. A genetic predisposition, something in the environment, and certain live viruses or bacteria. Many scientist think the Ebstien Barr Virus. Most rabies vaccines are not live so the likely hood of it causing the disease directly is not high. More likely you were set up for the disease genetically and possibly had the EBV which 98% of the population has and possibly the vaccine was your environmental trigger.
Rabies vaccines are given to keep people from contracting a disease which is almost always fatal so the benefit out ways the risk of MS which is not usually fatal.
Alex