After installing and configuring W3TC with wordpress 3.0.1, I started receiving "http error" from the flash uploader, and a blank page from the browser uploader. Everything else works great, and I love the speed from W3TC... anyways, I researched the main "image upload http error", and did everything described: fresh files, mon_security in .htaccess, ect... tried 100s of things nothing worked permanently.
The only thing that worked was to disable W3TC, delete .htaccess. Re-enable caching (new .htaccess)... Images uploaded fine! BUT ~ an hour later > HTTP error again... so caching interfering with upload? Bug in W3TC?
Let me know if its not just me! If its a bug, lets fix it :)
Site Ref: http://www.jamaicaskiteam.com