That is interesting MiniD. I've never seen a lamp ballast interfere with a computer to the point of causing a crash, but I can tell you they can be troublesome when trying to design and test high gain audio amplifier circuits and optical communication links (because florescent lamps flash 120 times a second when feed from a 60 Hz source).
"Old" design florescent lamp ballasts generate a fairly large EMF (electromagnetic field) around themselves. A computer case with insufficient shielding (like a computer case with a large window in it) or a computer which has an ungrounded powersupply/case (which could happen in an older house with only 2 wire outlets, using a grounded to ungrounded outlet adapter, improperly grounded outlet, etc) could be subject to interference from the ballast which could cause data corruption. In this case, a high impedance open drain/collector signaling bus could potentially be subject to induced voltages. An example of this is the IDE bus. With a very long IDE cable it might be possible for a lamp ballast nearby to induce an accidental '0', which could cause a system to crash.
