A: 

The url encoded file path looks suspicious to me. I read somewhere that iPhone file paths should be represented as URL these days, but I don't think spaces need to be url encoded.

Try removing the %20's from your path and trying again?

Jasarien
I let the file path be:**/Users/andrei/Library/Application Support/iPhone Simulator/User/Applications/0547AE74-AD10-4BEF-98CF-8FFF5BB2F70F/Documents/1280913694.caf**so, no %20, and now...which is weird, it tells me that the file does not exist (returns 0 at fileExistsAtPath), but also that the file is deletable (returns 1 at isDeletableFileAtPath).The error still remains and is not deleting the file.
Andrei
Could you please post the code you're using to retrieve the path?
Jasarien
posted in the original question as a second edit (**edit2**)
Andrei
Are you able to test this on the device to rule out some strange issue involving the simulator's application path?
Jasarien
Nope, I can't, I don't have a testing device, just XCode.
Andrei
I can't see anything obviously wrong in the code, so I don't know what to suggest other than trying to test it on a device, if you can get hold of one. A second hand iPod touch would be sufficient, and quite cheap.
Jasarien
In a terminal, try ls -l /Users/andrei/Library/Application Support/iPhone Simulator/User/Applications/0547AE74-AD10-4BEF-98CF-8FFF5BB2F70F/Documents/1280913694.caf and see what the permissions say. They should look something like this: "-rw-r--r--" followed by a number and then your username and "staff" as separate words.
Kalle