Can't get Yahoo working either. Link-local, MSN & AIM all working.

Yahoo was working until the pager issue described at your link - hosts fix worked for a bit, then stopped.

Tablet installation as follows:

libpurple0 (2.6.3-6nix0)
telepathy-haze (0.2.1-2)
rtcomm-beta-os2008 (2.4-1)

No longer anything in my hosts file to affect RTCOMM setup.

Adium logs into Y! without issue so problem an RTCOMM issue - not caused by Yahoo account (had failed to log into Yahoo for long enough that account was suspended - reactivating did not get it working again on tablet).

If you get a fix please post...