Possible to daisy-chain two HDMI switches?

Yes, assuming they are of good quality.

Yes, completely allowed and supported by the HDMI and HDCP specifications. I believe HDCP spec allows for up to 7 layers of daisy chaining. Keep in mind that the image may take a couple seconds longer to come up because each layer has to be authenticated serially. But once authentication is completed, you're good to go and shouldn't have to worry about it, so it's something you have to experience only during the power up.

I'm having trouble doing this with some players.

I can't get the following players to work if I have 2 or more hops:

Samsung BD-P1000
Philips BPD-9000
Sharp BD-HP20
Sony-S500

Every other player I have works fine through 2 hops, but these 4 wont work. It keeps trying to cycle and get the video but I end up with a blue screen or a black screen. I got the Sharp to work once but then it quickly cycled back to a green screen for that one actually.

Any thoughts?

The current setup is, players go to HDMI box, which then goes to another HDMI box which then goes to the monitor. If I hook up these 4 players to the 1st HDMI box in the chain, they work fine.

Its a work thing, thats why I have all the players, in case you were wondering

BTW, two of the switches are the 5 port monoprice ones, the other one looks identical but has a different label.