I've run into this problem in the past. CrashPlan is a great service, but slooooowww to backup, and their software is real fussy.

Anyway, first thing to try is this:

1. Open the CrashPlanService.ini, which resides in the same folder where CrashPlan was installed to on your computer. (open with Notepad).

2. Look near the top, where is says "Output File=". It shows where it keeps a log of what it's doing. By default, it should be "C:\ProgramData\CrashPlan\log\service_output.log".

3. Open that file in Notepad too, then look near the bottom. It should show you what the problem is.

Now,

Chances are pretty likely that at the bottom of that file it'll mention something like this:

There is an incompatible JNA native library installed on this system. To resolve this issue you may do one of the following:
- remove or uninstall the offending library
- set the system property jna.nosys=true
- set jna.boot.library.path to include the path to the version of the jnidispatch library included with the JNA jar file you are using

(Bold text added by me, because this is what we're going to address in this fix).

1. Go back to CrashPlanService.ini, and around line 11, where it says "Virtual Machine Parameters=", add this to the end of that line: -Djna.nosys=true

2. Save the file, overwriting if it asks.

3. Restart the CrashPlan Service: Right-click on your windows Taskbar -> click "Task Manager" -> Click the tab that says "Services" -> Look for "CrashPlanService" -> Right-click it and click Restart.

4. Start CrashPlan back up, it should connect now, without issue. *fingers crossed*