Until recently, I have been able to upload files up to 150 MB (customized PHP.ini settings). Now, if I upload an mp3 file I receive an "HTTP error" once the file is finished uploading. I am still able to use the Media Uploader to upload smaller .png files.
I checked the compatibility of my theme, and it was tested up to version 3.3. I switched to the Twenty-Eleven theme, and still encountered the same problem.
My site is hosted on Bluehost, and I have sent two separate requests for assistance to them that have received answers that weren't helpful at all.