Home page main menu issues w/cache

After testing my site http://test.corvetteclubsantabarbara.com for the past few days, I have discovered that after 1 full day of no modifications, the transparent header switches from a static main menu w/transparent background to a white background that scrolls along with the content (no longer static much like an iPhone display). The only solution is to clear cache (Comet Cache Pro) and the static main menu re-appears along with a transparent background. I did look @ the Comet Cache Pro settings and changed Cache Expiration Time from 1 day to 7 days but that will probably cause the same problem at day 7. Is this leading to a support question with Comet Cache or is this something within the Theme that is controllable?