i got the same problem as yours a month ago. but now the crawl is going up back http://forums.digitalpoint.com/showthread.php?t=808407&highlight=googlebot
"Googlebot last successfully accessed your home page on Apr 4, 2008" It updated today, now it says that Googlebot came on the 11 May. But I'm not worried because I know he comes every day. Its just that Webmaster tools does not update every day. When it does update, or even now, you can have a look In webmaster tools, Click on "tools". and have a look at your "set crawl rate" page, it says..."Number of pages crawled per day" and gives you a Maximum Average Minimum. That should tell you he is there every day. (unless your average is 0) If you want to know when the last time Googlebot came to your site then click "Tools" then "Analyze robots.txt" and you should see, "Last downloaded ? hours ago" Status 200 (Success). And also you can try clicking on "Sitemaps" "Overview" and you will see when that was last downloaded. (sometimes that takes a while to update to.) Generally you can see when he was last at your site by going to "Analyze robots.txt". Hope that eases any worries Cheers James