I just recently built an overo u-boot.bin image, and erased my nand memory using 

nand erase 240000 20000

After this, I re-booted the system and 

setenv defaultdisplay lcd43

but the changes don't take effect!! I had a fully functioning environment, just up until the point I erased my nand memory.

Now after rebooting and tying printenv, I noticed that the environment variables are not getting substituted at all. It still shows it with ${variablename}, instead of populating it with the variable name. 

mmcargs=setenv bootargs console=${console} vram=${vram} omapfb.mode=dvi:${dvimode} omapfb.debug=y omapdss.def_display=${defaultdisplay} root=/dev/mmcblk0p2 rw rootfstype=ext3 rootwait

What could be happening now? It used to work before!! How can I fix this?

Best regards,