lost pic link thingy

Hi all,
A few times now I have added to my own various threads in a post, usually containing a whole lot of blurb (which takes a while) and pics, at some point during the construction of the post, usually when I have attached them where I want them in the post and then I do a preview, when the page reloads the actual pic is gone and in its place is for eg [attachxxxxxattach] if I click on the attach thing it takes me to an error/missing link/cant find page:(( to fix it I have to delete the attach link thingy and reattached the pic which seems to fix things.
Is this a problem with my comp, me or the forum server or just the unknowns of cyberspace:? any thoughts.....


Thanks
Pete