CFURLResourceIsReachable failed because it was passed this URL that has no scheme

Question

I have a Cocoa program with the goal of deploying 10.7 using the latest (10.8) SDK, I run it on 10.7.5 with Xcode 4.6.2. In this I work with NSURL without any problems, everything works fine. One of the methods I use is the NSURL method:

[newURL checkResourceIsReachableAndReturnError:&error] 

with newURL a pointer to aNSURL. So far so good.

However, when I compile and run this, the following warning is installed on mac mini with Mountain Lion:

CFURLResourceIsReachable error because it was passed this URL that does not have a scheme

and some other things also go wrong, such as

 [dict setObject:url forKey:[url path]], 

with dict NSMutableDictionary and url NSURL, url is simply no longer added to the dict. Strange, isn't it? Am I missing a change in NSURL from OS X 10.7 to 10.8?

Sorry if this has already been discussed here (I could not find it), thanks for considering this issue,

Marein