It seems to be a compatibility problem with Zend Optimizer.
Disable Zend and apache don t fail:

;zend_extension_manager.optimizer_ts="C:/wamp\optimizer\lib\Optimizer-3.2.8"
;zend_extension_ts="C:/wamp\optimizer\lib\ZendExtensionManager.dll"

Confirmed with WinXP
PHP Version => 5.2.3 (May 31 2007 09:36:39)
PHP Extension => 20060613
Zend Extension => 220060519 
(i.e. xampp 1.6.3a for Windows)

Test class 'a.php':
<? class A { public function b() { print "a!\n"; } } ?>

Test file:
$fh = fopen('a.phb', 'wb');
bcompiler_write_header($fh);
bcompiler_write_file($fh, "a.php");
bcompiler_write_footer($fh);
fclose($fh);
print "compiled.\n";

bcompiler_load_exe('a.phb');
print "loaded\n";

$x = new A();
print "constructed\n";

$x->b(); // <-- Windows: Access Violation
// Debugger says: 
// Unhandled exception in zendoptimizer.dll, 0227e7be

Disabling 
"zend_extension_ts = "C:\xampp\php\zendOptimizer\lib\ZendExtensionManager.dll""
in php.ini makes the above work.

I'm pretty sure bcompiler won't work with Zend Optimizer.