Conflicting information on Google

Is there or isn't there cache?

[Talar]

If I search for my website’s homepage cache the result is: “Sorry, no content found for this URL”. However, if I search for a specific sentence taken from my homepage I find my website link and cache (below many less relevant results that simply link to my website), which indicates “This is G o o g l e's cache of [my homepage URL] as retrieved on 23 Sep 2005 23:00:13 GMT”.

This error is now causing my website to be almost impossible to find using almost any keywords, unless they match some exact complete sentences. Other inside webpages don't have the problem.

I have submitted a sitemap but it doesn’t seem to help. Why is Google indicating both that there is no cache for my homepage and that there is a cache? What can be done to solve this problem (it’s been like this since Aug/20)?