1G analogue mobile phones were a major problem...
Interesting, in the mid-nineties we did quite extensive testing for a period of about 3 months under CAA supervision with three pilots up front, making monitored Cat III approaches in VFR with 1G phones in various use configurations in the cockpit, no ILS issues were noted on any of the approaches. On the F70 we did have a couple of FMC resets which we suspected but could not conclusively link to phone interference, but that was all.