I can't upload a picture and an audio file

I have just tried to upload new picture and audio file, but I couldn’t do it. The error was shown. My browser is Firefox 3.6.8 on WinXP.

What steps did you use? And what was the error shown? I noticed that when I go to the site recently there are delays in the web page loading. Sometimes I am getting errors, but then I try again later and it works again.

Now I can upload pictures and audio files. Thanks.