Please note that N4G is aware of and has handled the recent issue with regards to the external linking of sites via N4G. The issue was found to be linked to a few other sites that had malware notices on their sites and were linked to by N4G.
At this time we are awaiting a review by Google to clear N4G of any issue. Once that is done, you willl be able to once again link to external sites without the malware warning notice.
Looks like everything is back to working order. Again, thanks for your understanding in this issue. ~cgoodno