Yep,
Seems to be a common problem. I have the same issues. If I push 2 buttons at once I can usually get it where I want but sometimes I have to restart the 4R to make it respond. Supposedly there is a guy who via ebay will fix them for ~$70 and folks have been happy with the results.
I think this is the link but read some of the reviews here on the forum to make sure:
1999 2000 2001 Toyota 4 Runner Limited Climate Control Repair Digital Heater AC | eBay
HTH
UtEp