This happened to me and it was because I had the legacy plugin active. Both the administration and front end were blank.
You need to ftp into your site and download configuration.php
Around line 32 is the following code:
| Code: |
var $dbtype = 'mysql_cached';
|
Change this to
| Code: |
var $dbtype = 'mysql';
|
And reupload the file. If you can't upload the file, delete it from the server first.
Your admin will be back but the front end gives an error message.
Login to the admin and Extensions -> Install/Uninstall and click Components then select QCache and click uninstall.
The frontend should now work - phew!