Pfui - 12:57 am on Feb 23, 2012 (gmt 0)
Is the unobfuscated IP one of amazonaws.com's?
See also a few additional UA variations here:
Amazon AWS Hosts Bad Bots [webmasterworld.com...]
For example (seen last week); space before paren is in the original UA:
SkimBot/1.0 (www.skimlinks.com )