Hi Roger,
The blank screen means you're getting a php error but you have
display_error set off in php.ini or in the boot path.
You may have an error in your login path, your session table may be
corrupted, you might be running out of memory on your server, or the
server may be having trouble setting a session cookie on your
browser. These are common problems.
Try adding
error_reporting(E_ALL);
ini_set('display_errors', TRUE);
ini_set('display_startup_errors', TRUE);
after the boot code in index.php
Also check your apache logs watchdog table to see if you're getting
errors.
--
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-Don Pickerel-
Fane Software