[LAD] Client connection to JACK fails with socket error -- help?

Hello all! My name is Simon, I am a long-time user of JACK on Debian-based Linux systems. I prefer to compile JACK myself so I always set the JACK-packages in Debian to "hold", remove everything from /usr and put my build into /usr/local. Starting with Debian 6.0 "squeeze" (Kernel is 2.6.38-1-686 #1 SMP), this seems to cause problems somewhere. I checked out jackdmp from SVN yesterday, build was ok. jackdmp starts up, QJackCtl is able to connect and the connection graph shows up. But any other client I want to use with JACK causes the following error: [snip] Cannot connect to server socket err = No such file or directory Cannot connect to server socket jack server is not running or cannot be started [/snip] My test client of choice is mplayer. (SVN r3418) I checked whether the runtime linker uses the correct libs: /usr/local/bin/mplayer libjack.so.0 => /usr/local/lib/libjack.so.0 (0xb718a000) This should be ok. The list of file descriptors for the running jack server is [snip] jackd 13063 simon cwd DIR 8,6 36864 146594 /home/simon jackd 13063 simon rtd DIR 8,6 4096 2 / jackd 13063 simon txt REG 8,6 22899 223189 /usr/local/bin/jackd jackd 13063 simon mem REG 8,6 145629 236929 /usr/local/lib/jack/jack_alsa.so jackd 13063 simon mem REG 0,16 82493164 2070826 /dev/shm/jack-1000-0 jackd 13063 simon mem REG 8,6 1153328 391304 /usr/lib/libasound.so.2.0.0 jackd 13063 simon DEL REG 0,16 2995543 /dev/shm/jack-1000-2 jackd 13063 simon DEL REG 0,16 2995541 /dev/shm/sem.hTRyxy jackd 13063 simon DEL REG 0,16 2070960 /dev/shm/sem.2Jamky jackd 13063 simon mem CHR 116,5 241895 /dev/snd/pcmC0D0p jackd 13063 simon mem CHR 116,6 241896 /dev/snd/pcmC0D0c jackd 13063 simon mem REG 8,6 1323460 246009 /lib/i686/cmov/libc-2.11.2.so jackd 13063 simon mem REG 8,6 116600 228035 /lib/libgcc_s.so.1 jackd 13063 simon mem REG 8,6 149392 245993 /lib/i686/cmov/libm-2.11.2.so jackd 13063 simon mem REG 8,6 30684 245999 /lib/i686/cmov/librt-2.11.2.so jackd 13063 simon mem REG 8,6 9736 246001 /lib/i686/cmov/libdl-2.11.2.so jackd 13063 simon mem REG 8,6 117367 245998 /lib/i686/cmov/libpthread-2.11.2.so jackd 13063 simon mem REG 8,6 958479 223178 /usr/local/lib/libjackserver.so.0.1.0 jackd 13063 simon mem REG 8,6 975012 214075 /usr/lib/libstdc++.so.6.0.13 jackd 13063 simon DEL REG 0,16 2070886 /dev/shm/sem.5FWprn jackd 13063 simon mem REG 0,16 1012 2070831 /dev/shm/jack-1000-1 jackd 13063 simon mem REG 0,16 70712 1906270 /dev/shm/jack-shm-registry jackd 13063 simon mem REG 8,6 113964 228057 /lib/ld-2.11.2.so jackd 13063 simon 0r FIFO 0,8 0t0 2070809 pipe jackd 13063 simon 1w FIFO 0,8 0t0 1906224 pipe jackd 13063 simon 2w FIFO 0,8 0t0 1906224 pipe jackd 13063 simon 3u CHR 116,7 0t0 241899 /dev/snd/controlC0 jackd 13063 simon 4u unix 0xece16900 0t0 2070957 /dev/shm/jack_(default)_1000_0 jackd 13063 simon 5u CHR 116,5 0t0 241895 /dev/snd/pcmC0D0p jackd 13063 simon 6u CHR 116,6 0t0 241896 /dev/snd/pcmC0D0c jackd 13063 simon 7u unix 0xece166c0 0t0 2070959 socket jackd 13063 simon 8u CHR 116,1 0t0 2555 /dev/snd/seq jackd 13063 simon 9u unix 0xece16000 0t0 2070962 /dev/shm/jack_(default)_1000_0 jackd 13063 simon 10u unix 0xf4c71200 0t0 2995537 /dev/shm/jack_(default)_1000_0 jackd 13063 simon 11r FIFO 0,8 0t0 1906200 pipe jackd 13063 simon 12w FIFO 0,8 0t0 1906200 pipe jackd 13063 simon 13u unix 0xf4f81440 0t0 2995542 socket jackd 13063 simon 17r FIFO 0,8 0t0 1906224 pipe jackd 13063 simon 18w FIFO 0,8 0t0 1906224 pipe [/snip] So the server apparently has sockets open -- question is why are clients except QJackCtl unable to connect to them? I am out of ideas. I basically recompiled everything from source a few times (including alsa-lib, libsndfile, jack, mplayer) and nothing changed. I appreciate any help on this problem. Thank you very much in advance! Simon --