For those with MyEclipse for Spring 8.5 who have the Adobe Flash Builder plug-in installed, there is an issue when upgrading to MyEclipse for Spring 8.6 that will prevent the IDE from restarting. It can be both avoided (and corrected) by removing the com.adobe.flexbuilder.feature.core.nl1.link from the dropins folder.
If you are upgrading, remove the file before starting ME4S, then perform the 8.5 to 8.6 upgrade. After that is complete, shut down ME4S, re-add the Adobe file, and restart.
If you have upgraded and ME4S won’t start, remove the Adobe drop-in, start ME4S, then stop and re-add the drop-in.