I think its the mem clock, will try and see what happens....

Do I need to flash back to old bios first? Or can I just flash again with some changes?

Thanks

Zcash is now less profitable than etc, I think people will start switching back over.

download it from the MEGA link instead.

What speeds could one expect off a 280x ?

I'm new to this whole ZCash thing, any and all links regarding it would be great.

How can I run 2 Claymore instances (one for eth and one for zec)? Currently they running, but there have a problem with the port, how can I change the port for one instance (sorry can't find option like that in the description)?

-mport   remote monitoring/management port. Default port is 3333, specify "-mport 0" to disable remote monitoring/management feature.
   Specify negative value to enable monitoring (get statistics) but disable management (restart, uploading files), for example, "-mport -3333" enables port 3333 for remote monitoring, but remote management will be blocked.
   You can also use your web browser to see current miner state, for example, type "localhost:3333" in web browser.