no real help to you but I can confirm that on my n900 I can use skype out to international numbers in USA/spain (both mobile & landline) no problems, both before & since PR1.2.

to eliminate possible causes:

1. first. skypeout to the problem destination from a PC (not n900). If that is consistantly OK then the n900 is suspect ....
- is skypeout on n900 working OK to other destinations?
- is normal voice calling OK from n900?

2. if skypeout from PC is not working either then it may be a problem with skype's route to your destination, or with the telephone being used by the person you're calling:

-can you skypeout to an international destination in a country other than the one that is giving problems? if so, can you skypeout to a different number in the SAME country that is causing problems? if that works ok too then get your problem contact to check their own landline/mobile. If they say it's OK verify by making a short call to them from a landline just to be sure. then repeat by calling them from your n900 on a normal voice call.

this is all obvious stuff just to narrow down what is going wrong, but until you can eliminate other possibilities its hars to help.

last thought - are you skyping on n900 over 3G or WiFi? if 2G that could well be contributing to your problems. if 3G, is the signal good? if WiFi, is your LAN bandwidth/latency etc. ok? (ave you recenty changed firewall settings or router? worth checking these out too ...