Fatal error (memory exhaustion) after enabling other modules

I've been running admin_menu beta3 for a couple of days now. After enabling the forum, acl, and forum_access modules, I got

( ! ) Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 574355 bytes) in drupal-6\includes\database.mysql.inc on line 301
Call Stack
# Time Memory Function Location
1 0.0007 69248 {main}( ) ..\index.php:0
2 5.5370 29119752 theme( ) ..\index.php:36
3 5.5374 29169232 call_user_func_array ( ) ..\theme.inc:658
4 5.5374 29169232 template_preprocess_page( ) ..\theme.inc:0
5 7.1972 30525016 theme( ) ..\theme.inc:1831
6 7.1972 30527784 call_user_func_array ( ) ..\theme.inc:617
7 7.1972 30527784 theme_closure( ) ..\theme.inc:0
8 7.1972 30527912 module_invoke_all( ) ..\theme.inc:1565
9 7.1994 30528472 call_user_func_array ( ) ..\module.inc:471
10 7.1994 30528472 admin_menu_footer( ) ..\module.inc:0
11 7.1994 30528472 admin_menu_output( ) ..\admin_menu.module:350
12 7.2031 30530336 menu_tree_all_data( ) ..\admin_menu.module:524
13 7.2542 31587776 cache_set( ) ..\menu.inc:839
14 7.2632 31876104 db_query( ) ..\cache.inc:109
15 7.2637 32163904 preg_replace_callback ( ) ..\database.mysql-common.inc:41
16 7.2637 32163904 _db_query_callback( ) ..\database.inc:0
17 7.2641 32451584 db_encode_blob( ) ..\database.inc:224
18 7.2641 32451632 mysql_real_escape_string ( ) ..\database.mysql.inc:301

I can recover by removing the admin_menu directory or by editing the system table. However, even after disabling and uninstalling the other three modules, clearing the cache, rebuilding the menu, etc., I had a hard time reenabling admin_menu without getting the memory exhaustion. After a lot of fiddling it finally fell into place and seems to be fine again.

Now I've tried enabling just the forum core module, and the memory exhaustion is back! It's persistent on admin/build/modules/list (i.e. refreshing the page doesn't help), but admin/build/modules/uninstall/confirm, for example (from the history list), is fine and says 'The menu router has been rebuilt.' After that I can go to admin/build/menu/list again, and things seem back to normal.

This is on PHP 5.2.9 (XAMP running on Win7/64). It may or may not be related to #560056: Administration menu fatal error on update.