I don't know if anyone else has noticed this, but there are a growing number of retards out there, posting things badly. If one of your filters hits one of these collections while using 'release name' option unexpected things may happen. Most the time, this just causes a weird name to be imported which is not too big of a deal. Sometimes the subject will be so badly mangled that altbinz will come up with a null release name. When this happens, altbinz will download the contents of the collection into the root of the default download path (not the path chosen in rss even)
Solution: if release name < 8 (or some other number), ignore releasename option (use subject). This may need to be tweaked depending on how many misses/false positives it gets. I don't think many release, format, group combinations will fit under 8 chars though.
