ndis0: link down after idle time

[Hendrik Spiegel]

That's what the kernel tells me during boot:
ath0: <Atheros 5212> mem 0xde100000-0xde10ffff irq 5 at device 9.0 on
pci0
ath0: mac 5.9 phy 4.3 5ghz radio 4.6
ath0: Ethernet address: 00:0f:3d:ab:9a:b6
ath0: 11b rates: 1Mbps 2Mbps 5.5Mbps 11Mbps
ath0: 11g rates: 1Mbps 2Mbps 5.5Mbps 11Mbps 6Mbps 9Mbps 12Mbps 18Mbps
24Mbps 36Mbps 48Mbps 54Mbps

Mine is also identified as the 5212. But I saw that my hardware version
is B2 and the firmware versionn is 3.1.6.

You do not seem to be the only one with your problem:
This guy gets the same message as you did, but it is supposed to be
fixed:
http://lists.freebsd.org/pipermail/freebsd-current/2003-November/014227.html

According to this link an European B3 does not work with linux either:
http://madwifiwiki.thewebhost.de/wiki/DLinkDWLG520

sysctl dev.ath
dev.ath.0.%desc: Atheros 5212
dev.ath.0.%driver: ath
dev.ath.0.%location: slot=9 function=0
dev.ath.0.%pnpinfo: vendor=0x168c device=0x0013 subvendor=0x1186
subdevice=0x3a13 class=0x020000
dev.ath.0.%parent: pci0

BTW: Are you German? I just wondered because your SSID was "deutschland"
in your initial posting.