The check to validate the pre is added somewhere in between 1.24 and 2.0.0. Your error is due to the config of pregroup. One can setup it in 2 ways and some apparently do it in the way its not intended originally
Lets give some examples:
Following case means that releasename MUST contain "-group" so that ioA can validate you are indeed in correct group(this is a check for those in multiple pregroups on same server). This is because vfs is set to "_/pre/*".
Pre_Group_0 = "group|mp3|/_pre/*|100|100|hubba"
Next case:
Pre_Group_0 = "group|mp3|/_pre/group|100|100|hubba"
Here is the way its ment to be. Ie vfs is locked with groupname. In this way the release can be named anything.
If this doesnt solve your problem. please send me a note on your settings in a message either here or on irc and well see what cause it.