Not exactly sure, could also be related to upgrading my 1.4.2 world ... but it seems the EU duplication bug is back with current beta build #113, all glass fibres on reactor melted and all those fully filled MFSUs exploded on me on first startup xDD
Reading the EU on both the transformer and MFSU states 630+ EU whereas my reactor seems to push the expected 320 EU only (I'm using 'The Beast' setup):