I'm experiencing a weird problem on StackPrinter hosted on Google App Engine.
It seems that the application can't reach several endpoints like Super User or Server Fault; Stack Overflow and other endpoints still works.

This WORK (Stack Overflow)
http://www.stackprinter.com/export?question=478760&format=HTML&service=stackoverflow&linktohome=false

This DOES NOT WORK (Super User)
http://www.stackprinter.com/export?question=52483&format=HTML&service=superuser&linktohome=false

WORKING sites list:
Stack Overflow
English
Meta Stack Overflow
Programmers
Ubuntu
CSTheory
Webmasters
Photography
OnStartups
Statistical
Wordpress
Phisics
Role Playing Tex
Homebrew
Unix

NOT WORKING sites list:
Gaming
Apple
Super User
Server Fault
Stack Apps
Web Applications
Ui
Android
Electronics and Robots
Mathematics
Cooking
GIS

It works on StackPrinter mirror hosted on Dreamhost; that indicates that it is probably a problem of connectivity from Google data centers to those particular domains/subdomains; looks weird though.

@Kevin, could you please verify if StackPrinter's calls reach SE server properly?
This can be easily tested on Top Printed page.

Anyone suffering this problem?

EDIT:
Follow this post on App Engine Google Groups.

EDIT2:
Stackauth site does not work too

EDIT3:
uhm, it still does not work for serverfault endpoint.
http://www.stackprinter.com/export?question=261&format=HTML&service=serverfault&linktohome=false