As reported by a user:
"when I click on "previous build" oder "next build" the buildnumber is added to
the url, responding in a 404.
Here an example:
I'm watching build 696 and want to go back to 695 the buildnumber is added
before the old buildnumber to the url:
http://ourbuildserver/hudson/job/ourproject/695/696/
goind forward is resulting in this url:
http://ourbuildserver/hudson/job/ourproject/697/696/"

Comments by another user:
"maybe your project name contains spaces?
which are converted to %20 ?"

My comments:
"It gets even more interesting.
Basically, ANY unsafe character in project name leads to the problems
with Previous/Next build links.

For example, any Russian letters or German ones (like u with two dots)
trigger the problem.

I have a rough patch that fixes the problem, but I'd prefer to wait
for Kohsuke to return and review it before posting it to the
repository.

Maybe a better fix would be to fix Stapler's Ancestor so that it
would always return properly quoted URL, rather than unquoted value
(currently, the behavior is unclear and is not specified in
javadocs)."