in case it helps...
I have the u-boot 4.27 with the pingto patch and squeeze in NAND (ubifs) and on SD (ext2/3) - kernel is 18.104.22.168.
After having suffered with the DENX u-boot and the 3.0 Kernels...don't know why...
I found this:http://www.technolust.de/?p=70&lang=en
so my environment is showing these settings. Take care when you copy and paste from the web page; the high commas and the 'x' in the addresses may casue some trouble on the plug - so either type on your own or use an editor to replace the highcommas and the 'x'es.
Much fun & success!