For whatever reason the NT Manager is not working in our environment, getting an error message "Snap-in failed to initialize. Name: -not available-" and then mentions a registry entry 'CSLID'. Is it possible to reinstall just the manager?

kindly post windows event log for the error above.

there is no entry in the event viewer.....

Although i am not a real expert on this , but just a sugesstion ... looks like mostly there is a issue with system files at O/S level, how about the possibility of running windows setup but choosing REPAIR option, that way you can it can go ahead and repair those critical missing/curropted files.

Again having said that it's easy , but in case if it's a Production box then it wont be a cake walk, you will have to do some precautionary steps.

also you may want to do some googling or try this url
http://www.progtalk.com/ViewArticle.aspx?ArticleID=15

ofcourse you need to identify the correct underlying dll and then register it... above url is just a example
Hope it helps

Learner