Now I have installed the Arduino driver (and the port is set in the IDE) the compile takes only a few seconds. I withdraw the remark about the IDE being old and cranky and make another one about pathological connection to the target hardware...lol
BTW, one thing I found after doing all this is, on the machine that hangs, the error message says "cannot delete core.a", when the compiler hangs.When I look in the proper directory [c:\~documents\......\build771899352394394.tmp], I indeed find file core.a left in there [usually .tmp directory files are erased] and cannot delete it. For some reason its attribute is set to DON'T DELETE UNDER ANY CIRCUMSTANCES, or somesuch. Truly bizarre.