apologies to all,

I caused the performance problem myself. I have this habbit of disabling extensions I accumulate ever 1-2 months. I remembered that I did remove a strange file called "ProxyApp" from the root of the system folder. I put it back from the backup and now everything works as always.

I reinstalled 2.7.1 and the installer log says the usual "
Custom Action: com.limegroup.install.SettingsTranslator
Status: ERROR
Additional Notes: ERROR - class com.limegroup.install.SettingsTranslator.install() Unexpected Fatal Error:"

thumbs up to those who suggested reinstalling MRJ.
Thomas