I had a similar problem on an old Dodge Van.  It turned out that the battery
cable was corroded. 

 >X-POP3-Rcpt: fzsimmon@dilbert
>Date: Sat, 21 Jun 1997 11:33:47 -0500
>Errors-To: gsker@lenti.med.umn.edu
>Reply-To: nleong@jps.net
>Originator: vanagon@lenti.med.umn.edu
>Sender: vanagon@lenti.med.umn.edu
>From: Norman Leong <nleong@jps.net>
>To: Multiple recipients of list <vanagon@lenti.med.umn.edu>
>Subject: Re: no start problem
>X-Listprocessor-Version: 6.0c -- ListProcessor by Anastasios Kotsikonas
>
>FoxhntrPat states:
>
>>Volks- my Diehard battery fluid is above the plates, the terminals look clean
>>& well connected.  No battery or other warning lights have come on, but I
>>guess they can't be counterd on.  Radio & CB work but turning key produces no
>>starting sound whatsoever.  I've been drifting down my hilly driveway to
>>jumpstart.  Am I right that my Tugboat ('90 syncro westy) doesn't have a
>>catalytic converter this would harm?   I'll plug in the trickle charger
>>(snip)
>
>I had a situation very similar to yours, albeit in a Toyota.
>Started it up, drove to destination, took care of business,
>jumped in, turned the key and...nothing.  Totally dead.
>Had the electrical system checked; no problems found.  Battery
>appeared to be OK also, but since it was one of those sealed,
>no-maintenance deals there wasn't much to do with it.
>I ended up getting an Interstate battery and getting some cash
>back on the DieHard, and the problem never returned.
>
>I'd check the voltage on your battery first; I think a "normal"
>charged battery is somewhere around the 12.4V+ range.  Since
>yours is dead and you're trickle charging it, I'd measure after
>it's sat around for a little while.
>Personally, I'd ditch the DieHard & get an Interstate, but
>that's just my opinion, and I'd only do it if I knew there
>was nothing wrong with the rest of the electrical charging
>system.
>
>Good luck
>Norman
>
>
Daniel L. Simmons
School of Law
University of California
Davis, CA  95616

Telephone 916 752-2757
FAX: 916 752-4704
EMAIL: dlsimmons@ucdavis.edu