There is one other issue that may be causing it. Did you apply any grease between the chip and heatsink? and if so Did you possibly apply Too Much. But I still think it is a bad psu.
a 115 volt psu is just a core with a single wire (L1)wrapped around it and then at certain places a lead is connected to supply a fixed current. There can be any number of these. In a 230 volt psu there is a core with a dual wire (L1 and L2) wrapping around the core where each wire is supplying a 115 volts when you flip the switch all you do is switch the L1 to the L2 line with the nuetral but it also allows to back feed the system and this bypasses the self protection shut down within the psu. This is where you can overload your mobo and cause it to fail or short out. On a good psu being switched to 230 will not harm anything as all it has done is switched input lines. In a bad psu a short or overload will cause it to auto shut down or blow a fuse to protect your equipment and when switched this bypasses the self protection that is built in.
