Not quite an installation problem, but I was running fine with ejabberd on Ubuntu feisty/server, and did the upgrade to the latest, hardy. All went well with the upgrade except for ejabberd, which runs (and even appears to connect to other servers) but all attempts at client login get back a "<stream:error>disconnected"
I must admit I am having a hard time finding out how to turn on extra diagnostics to see what's going on here. A dump of things with ejabberdctl shows the accounts are still properly registered, so any thoughts at what's up?
In ejabberd 2.0.0 and newer
In ejabberd 2.0.0 and newer it is possible to define the verbosity of ejabberd log file. By default it is 4. You can try to start ejabberd that way, and check if the log files report any error message. Then try to login and check again the files.
If that doesn't help, you can increase verbosity to 5, but be ready to surf a lot of text until you find some clue about the problem :)