Hi,
This appears to be a bizarre issue but I think someone out there must have also run into this, so here goes:
Some corporate networks (like my workplace's) are heavily firewalled, allowing only traffic on certain ports (http, ftp etc) with everything else blocked.
When Facebook set-up their chat XMPP access they had apparently thought of that and set-up chat.facebook.com on port 443 (as well as the default 5222), although they apparently never published the information (I found that out just by testing).
Up to PR1.2 you could therefore easily connect to facebook chat from your workplace: Go to settings --> VoIP and IM accounts --> Click your facebook profile --> Advanced Settings --> Change port to 443 and confirm.

With PR1.3, however apparently Nokia have created a special configuration UI for facebook (until PR1.2, the jabber configuration UI was used) that does not have the advanced settings button - no means of changing the port number! That sucks.

To overcome this problem, we need to revert back to using the jabber configuration UI for facebook. Here's how to do that:

1. Open the following file in your favorite text editor:
/usr/share/osso-rtcom/facebook-chat.profile
2. Look for the following line:
3. Change it to read as follows:
4. Save the file. IMPORTANT: If you want to make a backup copy of the file, make sure it is NOT in the same folder!
5. Repeat steps 1-4 for the following file too:
/usr/share/osso-rtcom/voip-support/facebook-chat.profile
6. Go to /usr/lib/libaccount-plugins/
7. Delete or move the file libfacebook-plugin.so.0.0.0 to a different folder.
8. Delete the symlinks libfacebook-plugin.so.0 and libfacebook-plugin.so to the removed file.
9. Reboot.
10. Enter the facebook settings and you will now have the advanced settings button again.