Hi there,
I am also having this blinking-cursor-no-boot issue, but no number is dislayed before that on my system, as far I can see.
What I did so far:
Tried to flash another (much older) version of the Clover ISO file, than the mentioned version 4961, I took it down to version 1995, but the boot behaviour was the same, a blank screen and blinking corsor.
By the way, only flashing my boot drive using Rufus worked for me, by unpacking the tar file I’ve got from sourceforge layer by layer using 7zip, until I’ve got the ISO file inside. This was because I had some issues using BDUtility, see below. With the Rufus method I had at least some files on the Clover boot drive.
BDUtility:
The thing with BDUtility was, that I got an error message (Error Run Extract Latest Clover Data Set) everytime while copying the ISO content. It resulted in a target drive with an empty CLOVER partition. I also tried other versions of BDUtility, in combination with different ISO versions, but same there. No matter which version of DBUtility or ISO file I am using.
My only difference I think is that I am using a SATA SSD plugged into a USB adapter instead of a flash drive, because I just happened to have no flash drive at hand, but a whole bunch of small size SSDs (120-256GB) and a USB SATA adapter laying around. The drive I was experimenting with is a 120GB Kinston.
My system:
My system where I was doing the flashing of the drive is the same which the Clover installations is intended for, and the same I am writing this lines with, an Acer Aspire M5811 Desktop PC from around 2009.
I really hope, someone can help me out, since this project seems to be still alive and kicking 
All the best,
Zoli