Recently I tried the wordpress plugin "Easy Restaurant Menu" plugin. I used the free version and it all seemed OK so I decided to get the full edition which allows multiple menus to be created.
I downloaded the full edition - which came double (or was it triple) zipped for some reason so had to be unzipped more than once before I was ready to upload the zip file!
The instructions in the readme said they advise that you delete the plugin directory from the wordpress site and then deactivate and re-activate the plugin. This seemed a bit wierd to me since how can you deactivate a plugin if you've removed it from the system (which perhaps you can do - I am not a wordpress expert yet).
So I thought there could be no harm in deactivating the free version, and then delete and replace.... WRONG!!!
I pressed deactivate and killed the site. Whatever I did I got "Out of Memory" error - at a limit of 23 meg or so. This killed both the front and back ends. I tried getting the php memory limit raised by my ISP (and adding "define('WP_MEMORY_LIMIT', '64M');" to my wp-config.php file) - but strangely it didn't affect the error - the system still ran out of memory as the same 23 meg.
THE FIX - How did I fix in the end?
I removed the restaurant plugin directory - no fix.
Then I removed other plugin directories until when I removed the last active plugin I suddenly got my site back. It same up with an error indicating that plugins had been removed - at least something has been gracefully coded.
I then installed the plugins again - and they all seemed to use the data in the database so I didn't need to do much reconfiguration.
COMMENTS ON THE PLUGIN
The restaurant plugin is now working ok... but as I used it I realised it had a few drawbacks...
You can define food items - but only for one menu and one category. If you want to use the same food item in a different menu you have to create a new food item.... pretty crappy really.
Also organising the menus is a bit of a pain. If you create a page for each menu called say "evening" and you put the "evening" menu on that page then you can get the page name followed by the menu name which looks crap. It wasn't easy to tweak the theme - and I didn't want to affect all pages, but there was no easy way (like a check box) to make the menu stop displaying it's name... I will have to dig into the code but that's just not the point for a plugin I paid for!