From LKML:

Subject: [patch] Linux 2.6.4 requires procps 3.2

Now that the /dev/pts filesystem uses 20-bit minor
numbers, a new procps is required. Version 3.2 will
work even if you don't upgrade glibc. Failure to
upgrade procps will leave you with a messed-up TTY
column when more than 255 or 256 PTYs are used.

http://procps.sf.net/