Sigh... I am writing this in hopes of maybe helping myself and others...

Current versions: Joomla 2.5.4 and K2 2.5.6

Error: K2_FILE_DOES_NOT_EXIST

I had it working on my development site but when I started putting everything on staging, it stopped working.

and... just checked my DEV site.. now I am getting the SAME error.. I am SO puzzled...

Even though the file is attached in both the front end and the admin end... it will NOT let me download it. Both give an error that file does not exist.

So... without ANY changes to the DEV site, it all breaks...

On staging, I checked/fixed the joomla database and reinstalled K2 over the current install.

Now... I can attach a jpg and I can download it from the admin end but the front end still gives me the error.

When I try:
JPG: downloads from the backend, not the front end
ZIP: downloads from the backend, not the front end
MP3: Shows up in the list but all columns are blank. Does not show in the front end as an attachment. The strange thing about the mp3s are that when I attach them from the server, they disappear entirely from the attachment folder.

My site is supposed to go live on May4th and this is a key element.. any advice would be greatly appreciated...

Some more background information:
Media manager:
1. I have added mp3 to legal file extensions
2. Changed path to files folder to media
3. Even added mp3 to the legal image extensions

K2 Media manager:
1. Change root attachments folder: media/k2/attachments

Okay... so I uninstalled Joomla and reinstalled it.
I then reinstalled K2 so right now I have Joomla 2.5.4 and K2 2.5.6
I also installed allvideos plugin v4.4

I have a FRESH install. I have not installed any other components, modules or plugins..

I ran several User Acceptance Tests (UAT) and found that if the file is already on the server and it is in an m4a, K2 deletes it. I have tried several other file formats.. mp3s work fine.

Is this a known issue with certain file types or did I really space a setting somewhere?

Checkout the XLS for details about my UAT

Okay.. before I put this on the bug list, would love for someone else to try and M4a as an attachment...

maybe it is just me and I would love nothing more because then I can troubleshoot ME and get it working lol

I experienced the same problem, but was able to relate it to pathnames with spaces. What worked for me was to add three lines of code to the file "administrator/components/com_k2/lib/class.upload.php". Even though one could have done it.