I have a Lenovo Thinkpad X60.
After upgrading to 12.04, first thing I did was get suspend to HDD back, because I don't use my battery a lot. So I did that.
After a while (about a week, I upgraded on release, not beta), maybe a week or so, I started getting black screens from time to time after waking it up from suspend to RAM. I never got that problem with suspend to HDD. As it only happens sometimes, I can't reproduce it. Sometimes it doesn't happen for a week (daily use, approx 2-6 wake-ups a day), then every single time.
The precise symptoms are as follows: normally I got a black screen with my cursor on it, which can be moved, no problems there. I can't interact with the system in any way except for turning it off on the 1/0 button. The weird thing is, the cursor seems to react to what I had opened when going into suspend to RAM, so for instance one day I had writer open and then my cursor was a "I" for most of the screen.
I only get this in 12.04, never had any problems with this in 9.04-11.10.