1- When trying to log in to yahoo messenger it gives an error that says “The application could not connect to the messenger servers. The servers may be busy, please try again.”
2- When trying to log in to your facebook account through facebook exporter for iPhoto you get a connection error that simply says “There was a problem connecting with facebook. Check your internet connection and try again”
For sure it is an internet connection problem. but one of the reasons for this connection problem is Proxies.
What I did was, I went to System Preferences -> Network -> Advanced -> Proxies. Disabled web proxy (HTTP)
My explanation: Yahoo messenger and facebook exporter connect (also) to http. so once this proxy was not working fine or was mismatch with other services, these applications could not connect to verify logins or initiate the authentication.
As I said; this is one of the possible reasons/fixes. but most likely it is always at the network settings side or load on the bandwidth like you download/streaming(youtube?) too many things at once. so make sure everything about these points is good.
MAC OS and application versions I have:
Mac OS 1.5.8
iPhoto ver: 7.1.5
Facebook Exporter for iPhoto ver: 1.0.6
Yahoo msnger ver: 3.0 (beta)