ENVI has never been very good with formats other than the native bil and tif. I have seen the behavior you mention, but it is inconstant and dependent on how the file was saved into an img format. It would be good to know how you are saving the file. I find it very unstable to just give output an img file extension. Your best bet is use the "Save File as ERDAS IMAGINE" export utility under raster management. I have never had a file go corrupt this way.
Your best bet is to just save a bil out of ENVI and import into ERDAS. You can also use the bil file(s) natively in ERDAS and save results as an img format. The ERDAS import/export filters are excellent and minimize issues with software back and forth.
ArcGIS is not quit as stable in this regard but, can read and operate on bil files, even saving img files. However, I often have files go corrupt, outside of ArcGIS. Even though you can supposedly control output characteristics of a file (bit depth, compression type) I find that ArcGIS often does not honor these specifications. As such, this is not a good software for handling format conversions.