CustomErrors does not work when setting redirectMode=“ResponseRewrite”

Question

In a old site, I was changing the way that CustomErrors works by adding redirectMode=\"ResponseRewrite\" (new in 3.5 SP1):

Answer 1

I found that the problem was in Error.aspx. Still can't find what was the actual error in error.aspx that causes the problem.

Changing the page to a static html file solved the problem.