All the advice you need appears above. My son and I have had a very frustrating morning trying to get rid of the "stuck on Loading..." problem. After originally trying the 1.18 kernel upgrade we then read our box which has the URL for an R4 SDHC. We then tried the 1.25 kernel for this version of the R4 but still to no avail. We then actually looked on the chip itself and although the box says R4 SDHC we have the R4 Deluxe. We downloaded the 1.20 kernel from the links above in the post by Nick and now all is well.

The trick for us - as a few have already stated above - was to find which version of the R4 we actually had and then download an appropriate kernel. Good luck!