Apologies if the is the wrong place to post this quirk/bug:
Write a new post. Enter an a href link such as:
and save the draft. WordPress causes a 503 server error, and the post does not save.
The following links works correctly:
but this does not (note the trailing slash):
So I presume that the problem is caused by a duplicate http in the link, but it isn't that simple.
Setup is 2.5.1 on Linux/Apache, with very little in the way of customization.