Ok, here's more details: I have a DIR-601 installed on two LANs, one up North and one down South, both hardware A1 and both set for remote management when installed.
Before going south some 6 months ago I updated my DIR-601/North firmware to 1.04NA and verified at that time that I could open my DIR-601/South for remote management.
While down south I updated that router's firmware to 1.04NA and then found that my DIR-601/North would not open (just showing those three question marks in diamonds). Unfortunately, I am in doubt as to whether my DIR-601/North would open before the DIR-601/South firmware update.
Now, back up north I find that my DIR-601/South will not open, viz. showing only them question marks in diamonds on a blank page.
So, seems to me like firmware 1.04NA rejects remote management calls.
Here's answers to your questions:
Internet Service Provider and Modem Configurations
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North: ISP service = DSL
North: Modem = NetVito, 5300 series (supplied by ISP)
South: ISP service = Cable
South: Modem = Scientific Atlanta (Cisco), DPC2100R2
PC 3rd Party Security Software Configurations
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Microsoft Security Essentials and Windows (XP laptop, Win7 desktop) firewall at default settings in use before and after the remote management problem occurred, i.e. testing worked OK before firmware 1.04NA.
PC Web Browser Configurations
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Browser, North: WinXP = IE8 and FF28, Win7 = IE11 and now FF29 (was FF28)
Browser, South: WinXP = IE8 and FF28
Also tested at both locations w. Win8.1 laptop, Win8.1 tablet, and Android player, all w. updated browsers. Same negative result!
Never fancied Opera !
Browser security add-ons were not changed or added to since remote management worked. Clearing browser caches now has no impact.
Router log-in page does not show. Only those little question marks in diamonds on a blank page. ���
Thanks,
....