i guess the same fix is done for php5+ by ZE2's post_deactive func, but it's not enough for php4
patch here

cvs diff: Diffing .
Index: xdebug.c

RCS file: /repository/xdebug/xdebug.c,v
retrieving revision 1.298
diff -u -r1.298 xdebug.c
--- xdebug.c 10 Feb 2006 14:44:55 -0000 1.298
+++ xdebug.c 14 Feb 2006 04:41:59 -0000
@@ -1165,6 +1165,12 @@
int function_nr = 0;
xdebug_llist_element *le;

• if (XG(stack) == NULL) {

• / in request shutdown /

• xdebug_old_execute(op_array TSRMLS_CC);

• return;

• }

• if (XG(level) == 0) {
  / Set session cookie if requested /
  if (
  @@ -1339,6 +1345,12 @@
  int do_return = (XG(do_trace) && XG(trace_file));
  int function_nr = 0;

• if (XG(stack) == NULL) {

• / in request shutdown /

• execute_internal(current_execute_data, return_value_used TSRMLS_CC);

• return;

• }

• XG(level)++;
  if (XG(level) == XG(max_nesting_level)) {
  php_error(E_ERROR, "Maximum function nesting level of '%ld' reached, aborting!", XG(max_nesting_level));