Something changed. The trick is not to make matters worse by recreating things.
Start by checking the folder var/cache below the document root (this is the folder that has index.php and the app folder. If var/cache folder. If exists and has subfolders likevar/cachemage---* exists and has subfolders like , rename mage---*var/cache, rename tovar/cachevar/cache.old` to var/cache.old.
Test if this fixes the issue.
If it doesn't, please specify what tools you have available to interact with the database. For example, does your hoster provide the phpMyadmin tool?
What we know from your report That it is very unlikely that the table is missing, unless you have not visited your site in two months or it has been running on an external cache and no one has tried to place an order.
That the table definition can be found or is cached in the DDL cache. When Magento queries a database table, it stores the definition of the table in the DDL cache, meaning Data Definition Language.
That your connection to the database works, or you would have a message about permission to the database being denied, invalid adapter or invalid username / password combination.
Possible causes
- Cache corruption
- Corruption of the "ibdata" file, causing MySQL not being able to find the data, while the definition in the ".frm" file is in tact.
- Local.xml has changed and it's prefix removed, but the timestamp of the file does not reflect it.