Hi Natalie,
You should try to turn on the debugging mode through config.php in your moodle directory.
http://docs.moodle.org/23/en/Debugging#In_config.php
Just edit the config.php file and add
$CFG->debug = 6143;
$CFG->debugdisplay = 1;
and save it.
Then, you will see the errors which prevent your page from loading.
Google it or you may ask here also about those errors.