I have had my Eureka moment...
I have two DGL-4300's on-site, one A1 hardware and one A4 hardware with both units now flashed to firmware v1.9.
Very long story short: It is the
MAC Address!! and also the hardware version on the 4300...
On the A4 unit, setting the MAC Address to the default (printed on the bottom) allows me to bring up
yourfoodstore.com every time, in every browser.
Oddly, the A1 unit with FW:1.9 and default MAC Address
STILL fails.
That kinda ticks me off a bit, especially if the one my mom is using is a A1, which would mean I'd have to trade her my spare A4.
Also, my DGL-4500 HW:A1 FW:1.02 when set to the default MAC Address,
works!
The practical upshot is, I have NO idea why the default MAC Address matters in my attempts to connect, but the moment I change it (power cycling the Cable-modem so that it recognizes the changed MAC) it fails. I can browse elsewhere, but that page consistently fails.
I am very pleased that I didn't have to upgrade my 4500's FW past 1.02, just typing in the default MAC Address from the bottom of the unit, and resetting things was enough so that I now can bring up the site.
Anyone at D-Link wanna trade me for one or perhaps two somewhat quirky units for two (or one really shiny one) that is much less quirky? Heh. I need to find out if my mom's 4300 will work with this fix, but I am hopeful. It was bought after my A1...
In conclusion: If anyone else is having this problem, try setting your MAC Address to the default, and if it's a 4300, you might also need to be at FW1.9. Sadly, if you are on the A1 hardware, you might also be out of luck.
Thanks again for the help, and hope this helps someone.
Hank