DownloadError (ApplicationError 5) via URLFetch

[MLTrim]

Hi there
I'm experiencing a lot of DownloadError (ApplicationError 5) on my
application (http://www.stackprinter.com).
URLFetch API can't reach several stackexchange.com subdomains like:

http://api.gaming.stackexchange.com/
http://api.webapps.stackexchange.com/
http://api.ui.stackexchange.com/
...
and also
http://api.superuser.com/
http://api.meta.serverfault.com/

the problem does not raise on subdomains like:
..
http://api.photo.stackexchange.com/
http://api.programmers.stackexchange.com/
http://api.onstartups.stackexchange.com/
...
or
http://api.stackoverflow.com/
for example

Everything was running pretty smoothly until last night when this
started happening.
The issue seems related to network connectivity between App Engine
data centers and the API endpoints I'm calling from the app.
I've contacted other developers on StackOverflow API that have apps
on Google App Engine and they are all in my same bad situation.

What can I do?
Is there support for this kind of problem or do I need to wait and see
(eventually it will be fixed)?

thanks
Michele