I'd like to preface this by saying that I, in no way, consider myself to be an expert on this type of thing. What follows is simply my own personal experience.
Just got a Razr Maxx last month. Moved from a Dinc, which I had rooted and was running CM7 on, so I'm somewhat familiar with the whole flashing routine.
So, when I got my Maxx, naturally the first step was to root and try to find a good rom, which I quickly discovered is far more difficult with Motorola devices than HTC.
Anyway, long story short, I rooted, installed Safe Strap and flashed Eclipse, which I like, but that's when I started getting the data drops. Just like everybody else, I live in an area with solid 4G coverage, but my connection dropped constantly and never did the 3G handshake. I will point out that I also work in a neighboring county where I can only get a 3G connection and that never dropped. Only the 4G LTE.
Rebooting, clearing dalvik cache and turning the data link on and off worked temporarily, but it would always drop again within an hour or less.
So yesterday, I used Safe Strap to switch back to the stock rom and kept the root. Ever since then, my 4G connection has been solid with no problems.
Again. I'm not claiming that I have any clue as to what's going on, but for me, it seems like the custom rom was causing it.
As much as I hate the stock rom, looks like I'll be sticking with it until ICS or a good variation comes out.