unknown action upgrade : annoying error !

Hi,
i've installed MT 4.31 on openbsd in a chrooted apache 1.3.
Everything is fine except a very annoying error which is about six times on ten i got the following error:
a blank page with the laconic message

Can't load error template; got error 'the loading of template 'error.tmpl' failed. '. Giving up. Original error was:
Unknown action upgrade
.
If i repost the action by refreshing a few time later; it may work...

If looked in the MT::App::CMS.pm module and the action seems to be defined here and point to the package/sub Tools::upgrade

        'upgrade'                 => {

            code           => "${pkg}Tools::upgrade",

            requires_login => 0,

        },

I've also looked in the MT::App.pm : the error is raised when the action's code handler isn't defined.

I dumped the $app var :

GOT Global_actions:$VAR1 = undef;
GOT Mode : upgrade  require_login : 0  
GOT App :$VAR1 = bless( {
	 'state_params' => [ '_type', 'id', 'tab', 'offset', 'filter', 'filter_val', 'blog_id', 'is_power_edit', 'filter_key', 'type' ],
	 'mode' => 'upgrade',
	 'author' => undef,
	 'vtbl' => {},
	 'cfg_file' => '/mt/mt-config.cgi',
	 'mt_dir' => '/cgi-bin',
	 'default_mode' => 'dashboard',
	 'return_args' => undef,
	 'is_admin' => 1,
	 'upgrade_required' => 1,
	 'mt_user' => undef,
	 'config_dir' => '/mt',
	 'request' => bless( { '__stash' => { 'App-Class' => 'MT::App::CMS' } }, 'MT::Request' ),
	 'apache' => bless( do{\(my $o = 2131447860)}, 'Apache' ),
	 'cookies' => {
					'mt_commenter' => bless( do{\(my $o = '-2022317956')}, 'Apache::Cookie' ),
					'commenter_name' => bless( do{\(my $o = '-2022317676')}, 'Apache::Cookie' ),
					'mt_user' => bless( do{\(my $o = '-2022318276')}, 'Apache::Cookie' )
				  },
	 'plugin_template_path' => '',
	 'query' => bless( do{\(my $o = '-2022318604')}, 'Apache::Request' ),
	 'request_method' => 'GET',
	 '__mt_path' => '/mt/',
	 'charset' => 'iso-8859-1',
	 'app_dir' => '/cgi-bin',
	 'cfg' => bless( { '__var' => {
									'' => undef,
									'commentscript' => 'comments',
									'staticfilepath' => '/htdocs/mt-static',
									'adminscript' => 'app',
									'mailtransfer' => 'sendmail',
									'cgipath' => '/mt/',
									'database' => '/mt/db/mt.db',
									'staticwebpath' => '/mt-static/',
									'sendmailpath' => '/usr/sbin/sendmail',
									'xmlrpcscript' => 'xmlrpc',
									'searchscript' => 'search',
									'objectdriver' => 'DBI::sqlite',
									'trackbackscript' => 'trackback'
								  },
					   '__settings' => { '' => { 'dirty' => 1, 'key' => undef },
										 'schemaversion' => {},
										 'adminscript' => { 'dirty' => 1 },
										 'mailtransfer' => { 'dirty' => 1 },
										 'sendmailpath' => { 'dirty' => 1 },