What was the version before the upgrade, and what is the version after upgrade?
I know (from experience) that CF8 has a serious issue with Java 7 u25 and later. Apparently, the geniuses at Oracle closed some default network permissions and it's a huge PITA to clear.
CF8 will not support Java 8.
It will only support up to Java 6, which means the issues you are getting is probably due to compatibility with the JRE.
I think 1.6.0_24 is the highest support version for CF 8