Keep getting message pop up "Error reading/writing file “com.apple.logic.pro.cs”: Logical end-of-file reached during read operation," and "The Preferences are not loaded completely. Save them to "com.apple.logic.pro.cs" anyway?" Using Logic pro 8. ???

You can safely delete this file - its the preference file for control surface settings - you haven't said whether you're actually using a control surface or not, if so, you will have to set it up again. A new file will be created when you fire Logic up again, but of course it will contain default settings. If you have a complicated control surface setup, remember to keep a backup copy somewhere in case any future problems arise.

Other than that, you really have nothing to be scared about - hopefully your problem is as simple as that and there isn't an underlying problem (a corrupt hard drive, for example). You seem concerned about losing work, so I guess you want to think about backing that up on a regular basis too. If you're saving your projects to your system drive, do get an external one for this. And also check that you have plent of free space on your system drive - you need to keep about a quarter or third of it free for your OS and programs to run properly (some temporarily stored files can be quite large).

Just to add...

Logic saves some preference files when closing, the freeze you experienced left a corrupted .cs pref file.

Or...... your system hard drive is close to being full and OSX swap files were using the remaining space and the pref file couldn't be saved. That's why CM mentioned having enough free space on your system drive. OSX can write many GB of swap files so you really do need to have pleanty of free space on the drive.