I have exactly the same problem. Custom ArcReader, including the ESRI.ArcGIS.RuntimeManager.Bind(ESRI.ArcGIS.ProductCode.ArcReader); line.
Works on some PCs, gives the error "ArcGIS version not specified. You must call RuntimeManager. Bind before creating any ArcGIS components." on other PCs.
The bind line is executed but it gives 'false'.
OS doesn't seem to be the issue. It works on some Win7s and fails on others, It works on some Vistas and fails on others.
Same for licences, works on some ArcInfo SU, fails on others, Works on some with no ArcGIS installed, fails on others.
Same for Version, works and fails on 10.0, works and fails on various SPs.
What do I need to do to get this working?
Regards
Filip