I also have an image that is 2200 w x 1399 h that I want to upload, however I'm getting a 500 internal server error message after I press Upload in the admin area.
Basically your error is being generated due to a memory and time out error. You need to increase the parameters in your config file (php.ini) in order to accommodate these larger images. The thumbnail generator needs a little more run time to execute. In the threads you search you will see the 3-5 parameters most people edit to allow this error to go away.
Ok, so I added the following to the php.ini file....but my question is, where do I put that php.ini file....which directory? Also, do I need to do anything with the .htaccess file?
I would do something more like the above and your php file is in the php directory. Or if you have a package like a LAMP or MAMP stack etc it will be there under the php directory found within those directories.