If I am using k2 for article and comment creation, will it corrupt the site if I am using another registration process besides joomla default registration?

Not really.

You can even deactivate the K2 user plugin. I suggest you try reordering/ disabling the K2 user plugin if you have any issues.

Just recapping what you have mentioned so I'm clear.

So I'm using love factory extension for the default registration process in Joomla 3.0, and k2 to build the articles and menu items. By deactivating k2 user plugin, this should fix my error 1064 and mysql issues, and allow me to use love factory registration as default registration and k2 to build articles and menu item