Ground or "earth" is a curious thing. In some equipment it provides a reference point for data. For instance a 1 could be 5 volts in referece to ground. Some equipment electronics do a good job at providing their own referece above ground and aren't as effected by a lack of ground, meaning you still satisfy all the laws of electrical conduction and still have a decent difference in voltage differential and everything is OK. What is most likely the problem, since I am assuming the lack of ground is not inherent when the surge outlet is plugged into the wall, is EMF.

ground wire does not normally carry a charge that could create an EM field.

or maybe the longer cord has more length to create an EM field?
You almost have it there but it's the opposite. A ground wire is there to provide a referece in advanced equipment AND whisk away noise that could be reproduced in transmission media. Basically you are sticking this long copper conductor onto your equipment with no way to shield it agains EMF in other forms that occur outside the conductor. Basically it's acting like an antenna and picking up some electrical disturbance. It could be bad contacts on the dryer or washer or even an improperly seated circuit breaker or loose electrical wire in an outlet. Who knows.

It's amazing that your equipment is that sensitive. When noise is induced; it becomes hard to distinguish between the noise and actual data signal.