Minor Website Fix

[login to view URL] This osCommerce site just out of nowhere started going blank screen. You'll notice that you can see the Home screen, but when you click on anything it just goes to blank screen. Need that working correct again. [login to view URL] This Magento site is working except for customer checks out with PayPal. After they checkout with PayPal my site gives them a message: Unable to initialize Express Checkout. The weird thing is though is that the payment DOES go through. I first get a email saying there is a transaction failure. (SEE SCREENSHOT) Then minutes later I get an email saying it went through and the IS posted in the PayPal account. :-/ The problem is what the customer sees with that error message as they will then go and re-do the transaction and end up paying twice and becoming mad. Also on this site in my admin, I'm getting a ! message: "One or more of the Cache Types are invalidated: Blocks HTML output. Click here to go to Cache Management and refresh cache types" Not sure if that's hurting the site at all, but would like you opinion and possibly just fix it if easy. PLEASE DONT BID WITHOUT READING