Actually, the specification depends
on the HW, not the IOS. In your case
I assume you are using the NM-4/8E/T1-IMA,
which does support 1.0.
http://www.cisco.com/univercd/cc/td/doc/pcat/mut1e1p1.htm#xtocid1
Regardless, the IOS you are using can
be providing you with problems; the
support for this NM came in 12.0(5)T, so
you may consider upgrading (maybe try the
latest 12.1 mainline) to see if that helps.