ral0 interface hangs with the message "No buffer space available"

[Yuri]

Here's additional information:

'netstat -m' output:
174/2931/3105 mbufs in use (current/cache/total)
68/1892/1960/25600 mbuf clusters in use (current/cache/total/max)
68/1114 mbuf+clusters out of packet secondary zone in use (current/cache)
0/1327/1327/12800 4k (page size) jumbo clusters in use 
(current/cache/total/max)
0/0/0/6400 9k jumbo clusters in use (current/cache/total/max)
0/0/0/3200 16k jumbo clusters in use (current/cache/total/max)
179K/9824K/10004K bytes allocated to network (current/cache/total)
0/0/0 requests for mbufs denied (mbufs/clusters/mbuf+clusters)
0/0/0 requests for jumbo clusters denied (4k/9k/16k)
0/14/6656 sfbufs in use (current/peak/max)
0 requests for sfbufs denied
0 requests for sfbufs delayed
25 requests for I/O initiated by sendfile
0 calls to protocol drain routines

ifconfig ral0:
ral0: flags=8c43<UP,BROADCAST,RUNNING,OACTIVE,SIMPLEX,MULTICAST> metric 
0 mtu 1500
        ether 00:18:f8:2e:40:25
        inet 192.168.0.10 netmask 0xffffff00 broadcast 192.168.0.255
        media: IEEE 802.11 Wireless Ethernet autoselect (OFDM/48Mbps)
        status: associated
        ssid "xxx xxx xxx" channel 6 (2437 Mhz 11g) bssid 00:0c:41:53:e6:71
        authmode OPEN privacy ON deftxkey 1 wepkey 1:40-bit txpower 50
        bmiss 7 scanvalid 60 bgscan bgscanintvl 300 bgscanidle 250
        roam:rssi11g 7 roam:rate11g 5 protmode CTS