I have a problem connecting to 2 Vino VNC servers (Linux Computers running Xubuntu) at the same time from other linux computers on my network.

The computers are Based on the ODroid U3 chip which is ARM based. When both of the ODroids are on the same network VNC fails, When I turn off one of them I can connect to the other, As VNC is the main display for these computers, this is important.

Here's the IFConfig for ODroid1 (The old ODroid U3)

eth0 Link encap:Ethernet HWaddr 1e:f6:d7:be:00:ad
inet addr:192.168.1.62 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::1cf6:d7ff:febe:ad/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:3261 errors:0 dropped:0 overruns:0 frame:0
TX packets:3286 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:578475 (578.4 KB) TX bytes:1550098 (1.5 MB)
Here's the IFConfig for ODroid2 (The new ODroid U3)

eth0 Link encap:Ethernet HWaddr 1e:f6:d7:be:00:ae
inet addr:192.168.1.64 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::1cf6:d7ff:febe:ae/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:146660 errors:0 dropped:0 overruns:0 frame:0
TX packets:174482 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:104504282 (104.5 MB) TX bytes:112083194 (112.0 MB)

One more note from my experience, if I turn the old ODroid and then connect the new one, I can reconnect the old and have a couple of minutes connected to both via VNC, however this eventually fails WIth the same error... here's the error I get via VNC when both Odroid's are online and I try to connect the new one:

03/04/2014 01:33:11 AM Pixel format for client tzvi-lap-linux.local:
03/04/2014 01:33:11 AM 16 bpp, depth 16, little endian
03/04/2014 01:33:11 AM true colour: max r 31 g 63 b 31, shift r 11 g 5 b 0
03/04/2014 01:33:11 AM rfbProcessClientNormalMessage: ignoring unknown encoding type -131072
03/04/2014 01:33:11 AM Enabling NewFBSize protocol extension for client tzvi-lap-linux.local
03/04/2014 01:33:11 AM rfbProcessClientNormalMessage: ignoring unknown encoding type -131071
03/04/2014 01:33:11 AM rfbProcessClientNormalMessage: ignoring unknown encoding type -131070
03/04/2014 01:33:11 AM rfbProcessClientNormalMessage: ignoring unknown encoding type -131069
03/04/2014 01:33:11 AM rfbProcessClientNormalMessage: ignoring unknown encoding type -309
03/04/2014 01:33:11 AM Enabling cursor position and shape (rich encoding) updates for client tzvi-lap-linux.local
[xcb] Unknown sequence number while processing queue
[xcb] Most likely this is a multi-threaded client and XInitThreads has not been called
[xcb] Aborting, sorry about that.
vino-server: ../../src/xcb_io.c:274: poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed.
Aborted (core dumped)
odroid@odroid-office:~$

Also todat I found out that I can still connect to the VNC server from my mobile phone so this might also be a client related issue

Why VNC on local network? I never felt I need VNC on LAN. What SSH cannot do can be done by running X apps remotely, this is a native feature of X, application and display do not have to be in same box. Just set the DISPLAY variable to whatever you want.