Strange iMac behavior ---> White screen at startup & other problems, restart seems to fix things.

[Black]

steve... wrote:
[quote=Black]
The 3.5" drive is plugged into wall power, right? Did you check that connection?

I've been making regular Time Machine backups with that drive so it did have power.

I also remembered that the second drive in the chain is FW 400, while the SSD is FW 800. From what I understand, that should be OK. One last try. You were plugging and unplugging things when you swapped your router. It's possible the electrical cord to the 3.5" drive was jarred (or continues to be jarred somehow.) Have you checked it since this started?

[steve...]

I had checked them since the problems started. It doesn't seem that regular time machine backups would be possible with a drive with poor plug connection.

[steve...]

( Update #2 )

I've experienced no problems since I removed the second FW drive from the chain (connected with USB instead). This morning's startup was completely normal with no glitches.