Which version of Tiki are you using?
And do you have files stored in folders on disk or in mysql tables?
I confirm that I discovered this serious issue in a production site of myself using tiki 10.x (svn ). This site of mine was upgraded in early january from tiki 9.x svn to 10.x svn. And when uploading some jpg images, they are not displayed, the image name seems to be truncated the extension (foo.jpg is converted into foo, it seems). And the error message in my case indicates a valid path (as it was working fine for a year in the server, etc.; no changes on that side; I doubled checked and perms are fine for apache to write in those folders, etc).
The hash corresponding to the file (as indicated in the error message shown in the browser) does not exist in the server, so it seems that the file does not get uploaded to that folder.
I don't know if this is the same as your case, but I list I wanted to confirm that there seems to be some issue in some cases, that might related to your issue also.
When a bug (or regression is confirmed), a bug report should be added in the Bug Tracker:
and if a bug looks very serious, a message to the devel-list might be apropriate (most devs are not in the tiki forums, but all are in the devel list. See lists.