I forgot to mention that in all cases I've been trying to connect, the version was matching on both ends. I got to test with a friend all those revisions:
5.0-321 on my gentoo box with 5.0-321 on his windows box - Failed to connect.
Same with 5.0 stable on both machines.
But 4.0-7840 on both machines worked. My friend reported that he couldn't connect Gentoo 5.0-321 from a WM into his 5.0-321 windows host.
After these things, I thought version mismatch was not the problem we were facing.
EDIT: Tested the last nightly revision 5.0-424 on both machines (my gentoo box and his windows box) and it is also failing to connect.
5.0-321 on my gentoo box with 5.0-321 on his windows box - Failed to connect.
Same with 5.0 stable on both machines.
But 4.0-7840 on both machines worked. My friend reported that he couldn't connect Gentoo 5.0-321 from a WM into his 5.0-321 windows host.
After these things, I thought version mismatch was not the problem we were facing.
EDIT: Tested the last nightly revision 5.0-424 on both machines (my gentoo box and his windows box) and it is also failing to connect.