I recently had the same problem, ive written a post about it on my blog, i suggest anyone who is having the same problem, you try a earlier version as paolo said.http://www.zenbix.com/cisco/how-to-fix-upgrading-blank-screen-on-cisco-ip-7961g-7941g-79...
I've noticed so many threads within the Forum with the same issue. Although, ive not found a solution to fix the issue. (Step-by-step). So many ideas but little information on what to do and how to do it. I'm getting exactly the same as what Andrew a...