when you reply to any thread, it appears a text box with a browse button so that u can upload a file, being valid extensions gif jpg png txt zip bmp jpeg rar. I had the same problem too, but i guess it's related to the number of posts u have..although i'm not sure about this though.
I still have a problem with attachments... it worked a couple times but since I can't get anything. They show to upload but they are not on my post?
They are jpg and below 50,000 bytes.
What am I doing wrong?