Uhm im not familiar with how to do a memtest and which program to do so, do you have a link to a program that will do the job?
1- Checked, it is not selected.
2- Will be hard as i don't have manuals anymore
3- Don't know how to run memtest, nor which program i use to do so. I could google but i have no clue on what sites are "safe".
But im fairly certain the sticks are fine, as i have gotten 4gb when placed A-B, A-C and B-C. (sticks ABC)
gigabytes site has your manual mate, not sure if your rev1 or 2, but heres a linkhttp://www.gigabyte.com/support-downloads/download-center.aspx?kw=GA-X58A-UD3R&ck=
Memtest, you download the program, then burn it as an iso file to a cd,
then boot the pc from cd drive and it runs, you can only test one stick at a time though,
*Non memtest method*<Easier imo
Might be better off taking your sticks all out,
try booting pc with one stick of ram at a time, if one stick in particular is causing problems, boot failure, hanging etc, its a good indicator that stick is bad,
repeat with all sticks you have