Occasionally, our church office manager will get an HTTP error when trying to upload the MP3 file (about 35MB) of the Sunday lesson. Last time, she handed off the file to me. (Tuing off plugins doesn't help.) I got it uploaded via FTP. Then I used a load-from-server plugin to "tell" WordPress the file was there. I've Googled this endlessly. Some people see this with image files; not our problem. Others have said the temp folder on the site may be full, but GoDaddy support didn't respond to my emailed question. Our max allowable upload is 50MB.
What would help me most is being able to get around the fact that our cheapo account at GoDaddy doesn't allow log access. If I could see more than the simple "HTTP error" text in the admin dashboard, I could do my own diagnostics.
