There is a size limit for attachments. Typical jpeg / png / gif formats 500 KB Gimp xcf is higher 2 MB, and a maximum number of 4 5.
You probably fell foul of those limits. If anything else give details of what / from where you are trying to post. Not always the end receiver causing the problem, I now have some issues due to my ISP screwing my wireless router up.
You probably fell foul of those limits. If anything else give details of what / from where you are trying to post. Not always the end receiver causing the problem, I now have some issues due to my ISP screwing my wireless router up.