FLV upload not working

Ok, after some digging into it, this is where I get:
In the function FileUpload in sites/all/modules/fckeditor/fckeditor/editor/filemanager/connectors/php/commands.php (around line 175), there's a check for
if ( isset( $_FILES['NewFile'] ) && !is_null( $_FILES['NewFile']['tmp_name'] ) )
before it gets down to the call to see if the extension is valid

If i upload a flv, both of these if checks (isset, is_null) return false, which seems a bit strange, as if i upload a swf, they both come back as true.

sigh, i look further, but if you know where to look at, i'd appreciate the heads up
thanks

At the minute I'm running it on localhost, using EasyPHP to set up everything (apache, mysql etc.)
As far as i can tell, it's only the flv that fails (though i haven't tried with a lot of file types).

Where it's failing is in the if check above - both return false for .flv, but true for .swf, even if i do one straight after the other

I traced it further back to upload.php, and everything checks out fine there, until the call to FileUpload(). I'm not sure what's calling upload.php (unless it's just the button press, so I can't go back further)

Ah! that works now, thanks Jorrit, that's saved me from taking a faceplant out the nearest window :)
Is there any chance of putting that in as an error message, so you get "file size too big" rather than "invalid file type"?

thanks again