I did some reading on the RFE website so to better understand what's going on. It seam the authors have built into it that "if" the rFactor exe is not a valid one, as in been cracked in any way the plug-in wont work. This is a fantastic thing and my hats off to them for it. So you can see now why the plug-in doesn't work for 1255C because that is exactly what has been done. The exe has been altered so now the RFE plug-in doesn't see it as a valid, legal copy.
Your not happy, Understandable, "But" it's comes down to this, and all your league members and admin are going to find it soon enough, that they will have to go to 1255C if they wish to continue using rFator1.
This is not ISI's fault! It's not the fault of RFE either. Both parties have done what was needed at the time. You and I have had to go to 1255C. I got a new PC and had no choice if I wished to continue. It was either that or not have rF1 at all. I prefer the latter!
Be happy ISI stood by their product and made the necessary changes so we all can keep using it. Be happy that RFE have done the right thing with their plug-in and made it only work in valid copies of rF1. Also be happy that RFE are going to stand by their product/s and update them to work with the new rFactor1 exe.
I also did find a 1255F exe on my external HD and installed it. It wont work even when I replace the license key from my old PC. Understandable!
The 1255 exe has the ISI content "but" some of the content hasn't got rfm files. The hammer and Howston. Not that their any loss but you could just create the needed files and they'd work.
1255C has all content working as well as a new addition. The Formula BMW.
http://rfactor.net/web/wp-content/themes/rf2011/images/main_feat_07sauber.jpg
There are reports of HDV and GBD mismatch and others have studied these and found them to be different. Again understandable. As a mod group member nothing we do ever is really final. We all continue to play with things to see if it can be improved. I'd say that this is also the case with the authors of ISI content. Meaning that now we should see 1255C as a updated version, more then just a replacement.