Hi @jpmenard,
The first problem maybe can be a problem of url rewrites.
I'll recommend you to reindex using the shell class located on:
/path/to/your/magento/shell/indexer.php
Then run:
php indexer.php reindexall
The second problem will need to activate the Magento's logs.
Enable Magento's logs
So then take a look to those logs (and also the webserver error log).
The idea is to find a clue to attack the issue.