The truth is, there is no way to know exactly what is going on without making formal inquiries - and sometimes not even then.
BUT: the fact that this is taking more than a month doesn't necessarily concern me. Often they need to request a file from storage, and even getting the file to the right officer can take a couple of months (by which time the officer has forgotten all about the case and needs to find time to review the file again to figure out the situation).
A few options: retain an attorney to make inquiries first by letter and then through the liaison system. Determine your congressperson, then contact their local office to ask the constituent services person to try to sort this out (input your zip code here: http://www.reichimmigration.com/node/241 to find your congresspeople).
You should retain counsel. There are avenues available only to attorneys to communicate with USICS on stalled cases. Without having reviewed the file, there is no way any attorney can determine if there is "anything wrong with [your] file."