Frequent 404 errors

I get this entry frequently in my 404 error logs:

…myblogpost+[PLM=0]+GET+http://mydomain/myblogpost/+[0,15952,22874]+->+[N]+POST+http://mydomain.com/wp-comments-post.php+[R=302][0,0,988]

Is it an attempt by a bot to spam?

Another bizarre thing is happening. While the following is a genuine call:

http://mydomain.com/wp-content/plugins/use-google-libraries/js/jQnc.js?ver=2.8.5

I get a frequent 404 request for this:

http://mydomain.com/wp-content/plugins/use-google-libraries/js/jqnc.js?ver=2.8.5

Similar 404-ed requests to other scripts also occur with non-capitalized filenames.

Could someone wise me up as to what is happening.

Thanks

S.K