I have the same problem. The WDR4300 v1.7 is not supported by any version of OpenWrt except the bleeding edge Barrier Breaker trunk, which is like the development version which hasn't come out yet as an official release. There are supposed to be fixes included in the code to fix up the problems with the WDR4300.
And AFAIK Gargoyle latest images and release 1.6 is built on the latest released OpenWrt which is Attitude Adjustment 12.09 final.
So it's' Catch22 for an "official" Gargoyle image.
As an optional method to install it, the Gargoyle documentation says that you can install OpenWrt and then install a set of packages, but the only URL I can find references what looks like a very old version of the packages:
src gargoyle
http://gargoyle-router.com/packages/kam ... theros-2.6
I've posted a query in this forum but haven't received any replies.
It doesn't look like the packages have been re-built against the latest OpenWrt SDK and made available.
I've been able to install the latest OpenWrt trunk on my WDR4300, and it looks like it works fine, although I haven't been able to test many config changes yet. It certainly didn't brick my box, which is a positive.
My choices now are two. I am tossing up whether to just install the packages using the URL above. There is a risk that the packages built against an older version of the OpenWrt SDK might be buggy or not work. The other option is to re-build the Gargoyle sources against the trunk code that I have installed. I have installed the OpenWrt code base and built an SDK, but I haven't had time to look at the Gargoyle source yet.
I'll post to you if I get any further.