I've never seen that message myself, but I personally think the P4 RC is a weak performer. In theory your issue doesn't sound like it's link related though. How close was your craft when you saw these warnings? I tend to agree with Stealthmatt.
Hey StealthMatt, have you seen this same warning message? You seem to know about it, but didn't say if you've seen it before.
Regarding the RC being weak, I constantly get quick disconnects and reconnects using the GL300C RC with my P4, even with windsurfer at moderate distances of 3000 to 4000'. Most of the time the "no signal" disconnect message is for a second or two and it relinks quickly. I have never got that message with my P3P, it just never happens. Sometimes my P4 will lose control links long enough to trigger RTH at moderate distances of 3000 to 4000'. Again, that has never happened with my P3P. Both Phantoms run chan#31 at 4mbps bitrate. My confidence has dwindled with my P4 so much that I took my P3P on vacation recently because I know it will perform, and it did. But 2wks ago I linked a GL658A Inspire controller to my P4. Oh man, what a difference. I've gone out 12,000' with no windsurfer at my normal flying area and didn't lose a bar.