postmaster hangs

Today i was trying to run an old ver. of an application on test server .
After a while i have got the pg hangs :
9899 ? S 0:00 postgres: [local] SELECT
9932 ? S 0:00 postgres: [local] SELECT
9933 ? S 0:00 postgres: [local] startup
9936 ? S 0:00 postgres: [local] startup
9941 ? S 0:00 postgres:
9974 ? S 0:00 postgres: [local] startup
9976 ? S 0:00 postgres: [local] startup
9978 ? S 0:00 postgres: [local] startup
9983 ? S 0:00 postgres: [local] startup
9989 ? S 0:00 postgres: template1 [local] startup
This a web application with apache connecting to post and doing things.
I have tryed to connect to the db with psql - nosuccess.
This the backtrace of 9989.
(gdb)
backtrace
#0 0xffffe410 in ?? ()
#1 0xbfffcc28 in ?? ()
#2 0x00000001 in ?? ()
#3 0x01488005 in ?? ()
#4 0x402ffffb in semop () from /lib/tls/libc.so.6
#5 0x08154d07 in PGSemaphoreLock ()
#6 0x08177ade in LWLockAcquire ()
#7 0x0816c7f2 in ReadBufferInternal ()
#8 0x08086eb0 in _bt_getbuf ()
#9 0x080882b6 in _bt_getroot ()
#10 0x0808ab62 in _bt_search ()
#11 0x0808aeca in _bt_first ()
#12 0x080894e0 in btgettuple ()
#13 0x081eba7b in FunctionCall2 ()
#14 0x08083f86 in index_getnext ()
#15 0x080836e4 in systable_getnext ()
#16 0x080f87ed in RelationBuildTriggers ()
#17 0x081e44ab in RelationCacheInitializePhase2 ()
#18 0x081f0ce5 in InitPostgres ()
#19 0x0817db30 in PostgresMain ()
#20 0x08157754 in ServerLoop ()
#21 0x08158d1e in PostmasterMain ()
#22 0x08128c21 in main ()

Version 7.4 something (does not remember and can't get it because can't
connect to the db).Trying to connect to the template also hangs up.
Please help.
Evgeny.