I am also having an issue with LinkPoint declining all my orders. I recently had my site scanned for PCI Compliance and after sending the failing results to my host they tweaked things and it passed. Well now my payment gateway is declining every card that is run on my site and LinkPoint said the requests are not even coming through.
I once again emailed my host and I received the following reply requesting additional information. The problem is, I have no idea how the gateway works which is what they are asking me.

Can someone please tell me what I need to tell them?
I am using 1.3.8a.
Do I also need the fix mentioned in this post? I haven't had any issues until this weekend.
Also... I use HostGator, in case some else is also experiencing the same issue. I have two sites on two different accounts and the same thing is happening on both sites.
The following is the email from them...

Can you provide us with some details on how your payment gateway works exactly? We have recently rolled out some new mod_security rules that could be blocking this, however, it appears that your domains hitting several of these rules, and as such make me believe that some of these are not false positives. Any insight would allow us to quickly determine what the cause might be so that we can assist in getting this working again.

Thank you in advance for any help.

Kelly