it checks for loss it packets all through the test, so that if during tests your getting failure it could be reporting that.
Also your mtu us low for cable - your on cable right?? Did you modify your mtu on your router?
So in my tests I get
The path between your network and our system supports an MTU of at least 1500 bytes, and the path between our system and your network has an MTU of 1500 bytes.
Yours was 1472 I believe which is low for a cable connection - now if you were on some sort of DSL type connection with overhead that would make more sense.
Trying to send data over your MTU is going to create fragmentation - should not be an issue, I would guess your router/firewall is blocking that. Why I don't know - misconfiguration I would gather, or you got something messed up in your MTU settings is causing that to be reported?
Pull the router out of the equation and redo your test and then post the results. I don't have that router to play with, but I gave you a couple of things to look at. That dynamic fragmentation setting and your NAT udp endpoint filtering settings.
edit: On my test I get this
The applet was able to send fragmented UDP traffic.
The applet was able to receive fragmented UDP traffic.
you had errors about both sending and recv'ing -- which is not a normally seen.
edit2: if you look at the client side transcript of the tests you will see something like this
001.576 test-3| Starting checkUDP
001.576 test-3| Sending UDP request to n1.netalyzr.icsi.berkeley.edu on port 1947
001.579 test-3| UDP socket at 192.168.1.100:60794
001.633 test-3| Got datagram of 50 bytes.
001.634 test-3| Can perform raw UDP access
001.646 test-3| Testing the ability to send a 1471B UDP packet
001.646 test-3| Sending UDP request to n1.netalyzr.icsi.berkeley.edu on port 1948
001.647 test-3| UDP socket at 192.168.1.100:60795
001.688 test-3| Got datagram of 25 bytes.
001.689 test-3| Can send a 1471B UDP packet
001.702 test-3| Testing the ability to send a large UDP packet (2000 bytes)
001.702 test-3| Sending UDP request to n1.netalyzr.icsi.berkeley.edu on port 1948
001.703 test-3| UDP socket at 192.168.1.100:60796
001.750 test-3| Got datagram of 25 bytes.
001.751 test-3| Sending UDP request to n1.netalyzr.icsi.berkeley.edu on port 1948
001.751 test-3| UDP socket at 192.168.1.100:60797
001.794 test-3| Got datagram of 25 bytes.
001.794 test-3| Can send UDP fragments successfully
001.794 test-3| Testing the ability to receive a 1471B UDP
001.794 test-3| reply from our server
001.794 test-3| Sending UDP request to n1.netalyzr.icsi.berkeley.edu on port 1948
001.799 test-3| UDP socket at 192.168.1.100:60798
001.835 test-3| Got datagram of 1471 bytes.
001.835 test-3| Can receive a 1471B UDP packet
001.835 test-3| Testing the ability to receive a large UDP packet (2000 bytes)
001.835 test-3| Sending UDP request to n1.netalyzr.icsi.berkeley.edu on port 1948
001.836 test-3| UDP socket at 192.168.1.100:60799
001.874 test-3| Got datagram of 2000 bytes.
001.874 test-3| Can receive UDP fragments successfully
See that it is sending and asking for larger than your MTU udp traffic - mine I get no problems, your there is some sort of issue with... Why??? I would guess your router. Lets see the test with your router out of the picture. Both with windows and with liveCD test would be best.