Comments not submitting, index not displaying

Hello!

I’m having problems with my installation of WordPress and I’m honestly quite confused about it because everything was fine until yesterday. Suddenly whenever someone submits a comment, it takes awhile to process and then transfers them to a blank screen, where the browser stops completely. After I submit a comment it does not display on the post or in my “awaiting moderation” or even my spam queue. Again, this problem began abruptly.

I also have a problem with accessing my website. Suddenly now when I visit my page the index says “Not Found” and tries to include the search form. The other pages also go down, and I figure this problem must be due to .htaccess because I have my WordPress installation in a folder, but have it so .htaccess points the blog to my index. When I re-upload my .htaccess file, everything goes back to normal, but the comment problem remains. My site also pulls the “Not Found” stunt when I visit it a few hours later too.

Also, when I edit a post in WP it now says “You attempted to edit a post that doesn’t exist. Perhaps it was deleted?” but the post does exist and the edits are still made.

I honestly have no idea what to do or how to go about fixing this problem. I have made a back up of my database, perhaps I should just reinstall it? Thanks for your time, and sorry if this has been covered before. I did do a search, but it was unsuccessful. ??