Quick update on this, looking at the logs it would appear that it is MSIE Crawler, within the last 48 hours it achieved 11,020 page views in just 2 visits.

For comparison:

Rank Spider Page Views Visits Hits Bandwidth (KB)
1 Yahoo! Slurp 56 54 56 679
2 Googlebot 88 42 89 796
3 MSNbot 24 12 38 1,067
4 Askjeeves 3 3 3 45
5 MSIE Crawler 11,020 2 11,278 128,512