this is quite bizarre, I've thought about your problem for some time but can't imagine how it could happen without some serious corruption in your system
have you done anything strange to the protections in /dev directory? if memory serves right, /dev/rtc is the real time clock device:
$ ls -la /dev/rtc*
crw-r--r-- 1 root root 10, 135 Jun 8 2005 /dev/rtc