Lazy Gbot, very old cache date of homepage

Gbot hardly reads any files, last cached version of start page outdated

[Bunjip]

Hi folks,

we've experienced similiar phenomenons as many webmasters:

a) Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html) reads tens of thousands of sites a day

b) real bot Googlebot/2.1 (+http://www.google.com/bot.html) activities have dropped from reading tens to 100s of thousands of sites until June this year down to a few hundred sites a day :-(

c) sitemaps have not had any positive effects yet.

d) hundreds of thousands of URLs dropped out of the Google index for no known reasons.

Additionally, the real Gbot has not visited our start page for almost two months now. The cached version of this start page reaches back to the middle of July. However, we do not discover other "slow death" symptoms .

Background:
- Quite well-known German based comparison shopping portal
- > 2 Mio. sites
- Google Tool Bar page rank 8
- website online since 2000
- strong natural back link structure

Has anybody experienced similar behaviour? Especially with his homepage or start page? Any new assumptions regarding those topics above?

Thanks for any hints or ideas,
Bunjip.