You should make sure your nandx driver or jr programmer drivers are installed correctly, follow simple instructions that are on the support page for those products. In Jrunner, you should notice the icon detecting the nandx or JR programmer if they are installed correctly.
I know the 4GB read, using the SD method can be tricky, I often have minor issues myself, but simple checks find the problem usually.
1. Make sure your device is connected with a good quality USB adapter and all the ports are clean (you'll never believe how much dirty port can affect this)
2. Make sure drivers are installed.
3. Using the 4GB qsb read kit, you need to have some patients, they way I do it seems to work for me
a. solder on 4GB QSB.
b. connect ribbon cable to qsb, then the other end, which looks like a micro sd.
c. hook it up to computer and have JF ready.
d. plug power to the xbox 360 ( do not turn it on )
e. (the most important thing) WAIT!, then, WAIT some more. (it could take some time depending on your computer.
f. The new drive should appear after a few seconds, but can take more time.
g. DO NOT click format, click cancel, or opposite of format, which ever message you get.
h. If that above appeared, it means you are good to read the nand, go in to JF and read the nand.
Bridging those resistors are not required to read the nand, if using a 4GB QSB, afaik.