There was a conversion problem in the initial release of Ledger 9.0C and setting the Active status on the Net Changes records. There was a service pack released in May 2010 that fixes this - either by using the Integrity Check and Rebuild within Ledger, or fixes the conversion from versions of Ledger prior to 90C.
I presume that it has been some time since you did the conversion, so doing a Rebuild after the Data Integrity Check, after installing the service pack, will be the solution. You can get the service pack
here from our website.