possible /lib was deleted or may be part of /lib. also hdd damages possible. if you don't touch anything in the past and sure that it is not result of hacker activity, you can do:
ask your DC or do it yourself - run manual fsck from local console or KVM
if above doesn't help - ask your DC install O/S resque CD - boot from CD and try download required files to apropriate folders. Then reboot from hdd.
If that doesn't help, try use restore/upgrade option from resque CD and when you done again try reboot from hdd.
If all of above doesn't help, you may ask your DC plug new HDD as primary and old HDD as secondary, and ask fresh installation for new HDD. Then you will have possibilities to save your old data and move it to new HDD.