barkingcat,
Can you give us more information on this?
1. Can you copy paste your installation details here? You can get them from MyEclipse > Installation Summary > Installation Details.
2. How did you install MyEclipse? Using all-in-one installer to download/using pulse explorer/installed eclipse classic and added MyEclipse plugin?
3. What is the JDK version in myeclipse.ini file located in your installation directory? Check for the value of -vm. To use JDK6, download the complete version and point the vm to the new location.
ME7.1.1 and Eclipse 3.4.2 are not compatible. To use ME7.1.1 you need to have an eclipse classic version installed on which, ME can be installed. If you want to use Eclipse 3.4.2, you can download ME7.5M1. This is a development version and the final version is to be released soon.