problems when trying to write post

I’m recently upgraded two sites to wp 2.6.1. One of the sites works fine but the other has a problem when I try to write a post, save a post, or edit a post. I get a message about a script not responding and I’m given the option to stop the script or continue.

If I stop the script the image uploader doesn’t work properly, if I continue it works fine but I want to get rid of the script problem all together. I’m guessing it has something to do with a file inside my wp-admin but I don’t know where to go. I also randomly get internal server error 500 for the same site.

Any help or suggestions will be greatly appreciated.