[tsac]

If the process is running a virus scan or some application is trying to do something , it can cause issues. All you can do is make sure nothing is running including the virus scan. check the task manager to see what is running. check the process use.

If all fails and you cannot get a clean load and you had the BB plugged into power during this, it may be a hardware issue.
Remember to let it complete no matter how long it takes, I did a wipe on a Z10 this week and the wipe and reset took over 1 hour. Slow yes but it worked.