I recently (finally) upgraded to Yosemite on my work laptop. One of the programs I use frequently - Adium - would not start up (froze immediately upon startup).

I found the issue - Bonjour announcement (enabled by default on Yosemite) seems to interfere with Adium. However - the fixes listed for this all applied to pre 10.10.4 Yosemite (i.e. when Yosemite was still using discoveryd).

I fixed up by editing my mDNSResponder plist file

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cp /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist ~
sudo plutil -convert json /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist
sudo vim /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist

When you edit the plist file, add “-NoMulticastAdvertisements” to the ProgramArguments array, so it looks like ProgramArguments":["\/usr\/sbin\/mDNSResponder","-NoMulticastAdvertisements"]

Then - convert back to binary and restart mDNSResponder

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sudo plutil -convert binary1 /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist
sudo killall -HUP mDNSResponder

Restart Adium (you may need to do force quit/kill -9), and all should be good