I noticed that my screen used to turn black and nothing was visible but the top status bar. I do not know if this is what you are speaking of though.
What kind of worked for me was finding a task killer that seems to know how to recognize the system apps on a Fascinate. The Samsung operating system MIGHT be MUCH different from any other phone in the programs it actually uses and for what. Like the whatever-viewer and an app called "daily briefing" that appears it might control a lot of tasks such as the Calendar and even the Clock/Alarm Clock settings.
After I downloaded Rhythm Task Manager and set it to ignore Daily Briefing, Phone, Messaging, Browser, Clock, Calendar so on and so forth, my Fascinate doesn't usually freeze much anymore because it's the only "Task Killer" I have found that MIGHT POSSIBLY know how to ignore the "built in" system apps that need to continually run on the Fascinate. There might be other "Task Killers" that work, but I wouldn't know, because the Rhythm Task Manager is only the 3rd or 4th one I tried where it seems to be one that might know how to work with the Fascinate - or I haven't had any issues with it as of yet in my experience but it is a "downloadable addon" app so download at your own risk.
Download anything at your own risk.
Also it seems that the Fascinate might be constructed with a BUNCH oh built in "safety whatever battery something saving features" to prolong battery life and prevent the phone from overheating. Like with the 3G network and the little "D" in the box. I can only assume that means disabled when the phone is not in use for internet purposes.
If I am running a bunch of Apps and the phone "freezes", if I shut the phone completely off and hook it to the charger, there will sometimes be a little yellow "warning signal" over the green charging battery with a "thermometer" next to it - I assume this means the battery and/or processor-phone were getting too hot.
I went into the Android Market and did a search for "Battery Status Bar" and there is one app made by Modded Logic (I think) that shows the exact percentage left of battery life in the status bar, but, can also be set up to show the phones "temperature".
Download any of this stuff at your own risk.