Centos5 Cant Mkdir Numeric Directories

We have a weird issue on one of our centos 5 servers, running the 2.6.18-53.1.4.el5 kernel

for some reason we cant mkdir any directories that are numerically named

ie mkdir 5789 doesnt work

alpha and alpha numeric work fine... ie mkdir ab567a

Quote:

[root@]# mkdir 6
mkdir: cannot create directory `6': No such file or directory
[root@]# mkdir 6ab
[root@]#

Someone suggested the adore-ng rootkit was to blame but we have run ossec root check, rkhunter and chkrootkit and even run clamav over the drives and cant find anything nasty