Bear in mind something that a lot of people do overlook,
The FDD cable has to be the correct way at BOTH ends, because of that twist in the cable that tells it which is drive A.
If the cable is incorrect @ both ends, then the drive light will be off, and BIOS wont complain about an FDD error, but you'll find that you'll get a seek error when attempting to use it. Swap the cable @ both ends and it's fixed.
If the light is on, then the cable is wrong at only one end - though which end is anybodies guess.
My PCChips mainboard had the keys on the wrong side of the HDD connectors, so red would go to where the board was clearly marked Pin40.
So although it's more likely to be the floppy, sometimes wierd stuff does happen