Cannot set env variable in u-boot

Hello,

i want to save some options in an uboot variable:

setenv optargs 'omapfb.mode=dvi:1280x720MR-16@60'
saveenv

It shows:
Erasing Nand..
Erasing at 0x260000 -- 100% complete.
Writing to Nand .. done

but when i reset and i use "printenv" to show me the env-variables it
shows:

optargs=

Whats the Problem ?
Have i bricked my nand?

Regards
rubiktubik