Paypal IPN not getting orders in ZC, no error msgs in logs

[maffud]

--- background info ----
ZC 1.3.8a (fresh install last year)
Added - Googlecheckout (Paypal IPN worked successfully after Google Checkout was installed)
Customizations - customized for layout and images through language files
I do not think this is a hosting issue, as nothing has been changed with the host and this was working a couple of months ago.
Not sure how long it has been down - I do not get many sales through my online store. First failure was seen yesterday. I have not been able to get it to work properly since I recognized the problem.
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Using Paypal Website Payments standard (IPN)
Symptom: Paypal payment notification is received via email, but the store shows no sign of the order (customer info is there).

I turned on debugging for Paypal IPN. I then tried placed several orders (paying with a second paypal account). It appears that Paypal is continuing to send and resend the notifications of the sales and subsequent refunds back to my store, but for some reason they are not being processed.

After making payment in Paypal, buyer is never returned to the store. Browser says it is trying to load the page from the server, but it never responds. After several minutes, a blank page is displayed.

Attached are sample log files (I removed some personal info but the relevant stuff is untouched) from the /includes/modules/payment/paypal/logs folder. If there is a way to get more detail in these log files, please enlighten me on how to do that.


Thanks in advance!