hello,

similar problem has been reported but without backtrace, so here it is:
(gdb) where
#0  0x29f1a1 in kill () from /lib/libc.so.6
#1  0x80c0398 in _erealloc (ptr=0x8686b24, size=1515870827, allow_failure=0,
    __zend_filename=0x81f5fa0 "zend_operators.c", __zend_lineno=903,
    __zend_orig_filename=0x0, __zend_orig_lineno=0) at zend_alloc.c:230
#2  0x80ca372 in add_string_to_string (result=0x7fff81d0, op1=0x7fff81d0,
    op2=0x7fffe5c8) at zend_operators.c:903
#3  0x8125a29 in execute (op_array=0x85e6364) at ./zend_execute.c:1448
#4  0x8127dcf in execute (op_array=0x85c304c) at ./zend_execute.c:2100
#5  0x8127dcf in execute (op_array=0x85e68a4) at ./zend_execute.c:2100
#6  0x80b8bd0 in php_execute_script (primary_file=0x7ffff834) at main.c:1200
#7  0x80d773c in apache_php_module_main (r=0x82cb614, fd=269,
    display_source_mode=0) at sapi_apache.c:93
#8  0x80b4662 in send_php (r=0x82cb614, display_source_mode=0,
    filename=0x83e77cc "/web/genesis/luza/zobraz_rubriku.php3")
    at mod_php4.c:512
#9  0x80b46a4 in send_parsed_php (r=0x82cb614) at mod_php4.c:524
#10 0x8142c13 in ap_invoke_handler (r=0x82cb614) at http_config.c:532
#11 0x815279d in process_request_internal (r=0x82cb614) at http_request.c:1215
#12 0x8152801 in ap_process_request (r=0x82cb614) at http_request.c:1231
#13 0x814bcb4 in child_main (child_num_arg=0) at http_main.c:4268
#14 0x814beed in make_child (s=0x826bd34, slot=0, now=960142178)
    at http_main.c:4436
#15 0x814c187 in perform_idle_server_maintenance () at http_main.c:4600
#16 0x814c5db in standalone_main (argc=4, argv=0x7ffffb64) at http_main.c:4832
#17 0x814cb1b in main (argc=4, argv=0x7ffffb64) at http_main.c:5093

	hope that helps,
		Michal Vitecek