Hello!!
I have joomla 1.5.26 and ms 1.2.86 (before have joomla 1.5.22 and old ms (it worked fine)).
I put the new version, but have this problem, and i dont know way, i upload all new joomla and put new files, but the problem is the same:
after the login the index administrator is in white (i cant see "control panel"),
when i write the component, module... url work fine.


I see it when have error in /administrator/index.php:


500 error


Call stack
# Function Location
1 JAdministrator->render() /var/www/mypage/administrator/index.php:109
2 JDocumentHTML->render() /var/www/mypage/administrator/includes/application.php:162
3 JDocumentHTML->_parseTemplate() /var/www/mypage/libraries/joomla/document/html/html.php:265
4 JDocumentHTML->getBuffer() /var/www/mypage/libraries/joomla/document/html/html.php:402
5 JDocumentRendererModules->render() /var/www/mypage/libraries/joomla/document/html/html.php:190
6 JDocumentRendererModule->render() /var/www/mypage/libraries/joomla/document/html/renderer/modules.php:41
7 JModuleHelper->renderModule() /var/www/mypage/libraries/joomla/document/html/renderer/module.php:84
8 require() /var/www/mypage/libraries/joomla/application/module/helper.php:173
9 JDatabaseMySQL->loadResult() /var/www/mypage/administrator/modules/mod_jpadmin/mod_jpadmin.php:44
10 JDatabaseMySQL->query() /var/www/mypage/libraries/joomla/database/database/mysql.php:355
11 JError->raiseError() /var/www/mypage/libraries/joomla/database/database/mysql.php:231
12 JError->raise() /var/www/mypage/libraries/joomla/error/error.php:171
13 JException->__construct() /var/www/mypage/libraries/joomla/error/error.php:136

It seems that you have a module "JPAdmin" that try perform an access to the DB and that it gets an error.

Verify your DB connection parameters.
As you can not login, check you "configuration.php" file and its DB connection (login, password, ....)

Another solution would be to use PHPMyAdmin to disable the JPAdmin module to get the access to you back-end.
This will give you the opportunity to see the configuration of the JP Admin module.