Blue Icicle

This is highly unusual. Have you checked Preferences -> Audio -> Devices in Logic Express? It must show Core Audio tab there and you can select your interface in Device. Make sure your interface is properly connected (it won't be an issue if you can use it with GB though).

Did you connect it BEFORE or after you launch Logic?

Does it have a driver which you could re-install?

Have you tried using another USB-port?

I am convinced it is something really simple, mate. Like a faulty USB cable, or some setting you overlook in Logic. Anyways, it's time to fork out Icicle's manual and Logic's manual and do some reading. There is so much I can do to help...

If it works with GB then it MUST work with Logic, especially if it doesn't use any specific drivers of its own.

I don't use this device, but here's what I think might help:

1) With the device plugged in, go to System Preferences → Sound. It should be in the list as one of the options under 'input.' It might be named "Blue Icicle" or even "unknown USB device." Select it for input.

2) Now go to Utilities Folder → Audio/MIDI Setup → Audio Devices. From the Audio menu, choose Aggregate Device Editor. Click the "+" and choose Built-in audio, or built-in output, depending on your machine. This will add a device that has two outputs (and maybe two inputs) Then select your Blue device, as it's named in (1) above. Depending on your machine, you now have an aggregate device with a total of 1 or 3 inputs, and two outputs.

3) Name this new aggregate device. Now open Logic, and select the new virtual device you just created in Preferences → Audio → Devices. When you select an input in Logic, depending on how you set up your aggregate device, it will show up in a Logic audio channel strip as input 1 or input 3.

That should work. Further reading here if you need more detail:

http://support.apple.com/kb/HT1215
http://support.apple.com/kb/TS2648