I don't have Windows but I tried your procedure on my iMac OS X 10.6.8 running LR 3.6. It worked properly. I tried it on several different files with solo mode turned on and also turned off.
I think the Adobe forum where you are also discussing the problem is more appropriate and more likely to result in a fix or workaround. As someone else mentioned, the problem doesn't occur in the LR4 Beta so it's unlikely Adobe will fix it at this late stage of the LR3 lifecycle.
Here are a couple of workarounds for you:
1. Avoid using that sequence of steps. That may sound like a stupid suggestion but ...
2. I nearly always apply a few common keywords to files during import. (I had to go back a ways to find a file that had no keywords in order to test your procedure). All the files in virtually every import usually have something in common that you can keyword on import. For example I was out walking my dog and taking pictures in the local conservation area this afternoon so on import I applied the keywords winter, snow, outdoors & Tiffin (the last being the name of the location) But I didn't include Mason (my dog) because he wasn't in all the pictures - I did select files and apply that one after the import.
3. Apply at least one keyword before you go to the Metadata panel.
I hope that helps. Good luck with your problem.
