It looks like your site is pretty dynamic, so that doesn't appear to be the problem. Could you have been banned for any reason? Are you using any black hat SEO techniques? (i.e. cloaking, etc?) How many other sites are linking to you? When I do a link: on Google, it doesn't look like very many at all. That is most likely your problem. A huge factor to how in depth google spiders your site and how frequently they return to your site, is how many other sites link to you.
cscgal
The Queen of DaniWeb
19,421 posts since Feb 2002
Reputation Points: 1,474
Solved Threads: 229
Getting incoming links is critical to good rankings. The more backlinks you have, the higher the pagerank - which means the more frequently google will respider your site, and the deeper they will crawl on each visit. (It doesn't influence your rankings, it just influences how many of your pages are spidered, which seems to be the problem.)
What could be possible is a particular reallllly high ranking page linked to you for a short period of time, convincing google that your site was worthy of frequent and deep crawling. But then that site removed you for some reason or another.
Either way, good luck! And get that backlink campaign started! ;)
cscgal
The Queen of DaniWeb
19,421 posts since Feb 2002
Reputation Points: 1,474
Solved Threads: 229