Sorry, the problem seems to have been that php.ini indicated that a browscap.ini file was available when in fact it wasn't.
So it's not a severe bug, but dumping core because a peripheral config option is poorly set seems to be a bug in itself.
Just in case it's still worth worrying about, here's a backtrace:

bt
#0  0x281edaeb in sapi_apache_send_headers (sapi_headers=0x2827bee0)
    at mod_php4.c:226
#1  0x281c91f3 in sapi_send_headers () at SAPI.c:435
#2  0x28227ce1 in php_header () at head.c:86
#3  0x282444c5 in php_ub_body_write (str=0x28246bb3 "", str_length=0)
    at output.c:314
#4  0x28244160 in php_body_write (str=0x28246bb3 "", str_length=0)
    at output.c:105
#5  0x281c27af in php_error (type=2, 
    format=0x28245a3c "Cannot open '%s' for reading") at main.c:386
#6  0x281c3ff1 in php_minit_browscap (type=1, module_number=1)
    at configuration-parser.y:252
#7  0x2821693d in php_minit_basic (type=1, module_number=1)
    at basic_functions.c:609
#8  0x281e4990 in zend_startup_module (module=0x282699e4) at zend_API.c:698
#9  0x281c2e48 in php_startup_extensions (ptr=0x28265d18, count=6)
    at main.c:716
#10 0x281c3ad1 in php_startup_internal_extensions () at internal_functions.c:59
#11 0x281c30ed in php_module_startup (sf=0x2826636c) at main.c:863
#12 0x281edbf8 in php_apache_startup (sapi_module=0x2826636c) at mod_php4.c:265
#13 0x281ee569 in php_init_handler (s=0x80a5034, p=0x80a500c) at mod_php4.c:660
#14 0x80555e9 in ap_init_modules ()
#15 0x805ee41 in main ()
#16 0x804e839 in _start ()

This should be fixed in latest CVS.
Please try it out. If the problem persist, reopen this bug report.

--Jani