I have 3 ZyXEL Homeplug AV powerline adapters as per the one in the review below.

I have two plugged in currently, one into my Be / Thompson wireless router, and one into my desktop pc (box1). every now and then the link indicator on the adapters (the mains link, not the ethernet link) goes nutty, and performance falls off a cliff (see below).

http://www.gadgetspeak.com/gadget/article.rhtm/753/479266/ZyXEL_PowerLine_HomePlug_AV_PLA401.html

64 bytes from box1 (192.168.1.101): icmp_seq=1064 ttl=64 time=996 ms
64 bytes from box1 (192.168.1.101): icmp_seq=1065 ttl=64 time=549 ms
64 bytes from box1 (192.168.1.101): icmp_seq=1066 ttl=64 time=6.15 ms
64 bytes from box1 (192.168.1.101): icmp_seq=1067 ttl=64 time=1400 ms
64 bytes from box1 (192.168.1.101): icmp_seq=1068 ttl=64 time=812 ms
64 bytes from box1 (192.168.1.101): icmp_seq=1069 ttl=64 time=11.1 ms
64 bytes from box1 (192.168.1.101): icmp_seq=1070 ttl=64 time=1185 ms
64 bytes from box1 (192.168.1.101): icmp_seq=1071 ttl=64 time=501 ms
64 bytes from box1 (192.168.1.101): icmp_seq=1072 ttl=64 time=1975 ms
64 bytes from box1 (192.168.1.101): icmp_seq=1073 ttl=64 time=970 ms
^C
--- box1 ping statistics ---
1074 packets transmitted, 394 received, +487 errors, 63% packet loss, time 1082497ms
rtt min/avg/max/mdev = 5.945/598.452/3526.454/639.768 ms, pipe 4

Any idea how to diagnose/fix?

I'm on linux so installing the windoze software that came with them is not something I'm terribly keen to do.