Brian's Brain

Earlier this morning (and notably before a single drop of coffee had even entered my system!), I solved a computer problem that's been bugging me for more than a year. I thought I'd pass it along in case some of you out there are experiencing similar frustrations.

As I mentioned, for example, in my mid-November 2007 feature article, I've got two webcams in operation here at the home office; an 802.11b-and-CAT5-supportive D-Link DCS-5300W and a newer DCX-5300G with 802.11g capabilities. The cameras' video feeds employ ActiveX controls, so they require Internet Explorer if I want to view their captured images via a web browser interface. Alternatively, I can always use the standalone Windows-only D-ViewCam utility to monitor them...assuming, that is, that it's installed on whatever computer I'm in front of at the time...

Unfortunately, as I also mentioned in last November's print writeup, Internet Explorer connectivity to the webcams' built-in web servers has been hit-and-miss. On some computers, it works fine. On others, even those using the identical fully patched versions of Windows and IE, I get nothing but 'HTTP 400 Bad Request' errors.

Historically, I've been able to work around the issue by alternatively using the IE View extension in Firefox, which accesses the IE 'engine', in combination with repeatedly refreshing each frame of the webcam-served HTML page until it eventually appears. But since I'm now running Window virtualized via VMware Fusion v2, Firefox for OS X is my primary browser. IE View only works with Firefox for Windows.

Past Google searches for a cure have been unsuccessful. But, after once again experiencing problems while traveling last week, on my virtualized copies of Windows XP and IE 8, and after webcam access had initially worked fine (thereby suggesting that some unknown software package I'd installed in the interim was the culprit), I decided to try Google once again. This time, I hit pay dirt. A blog post published just a week and a half ago led me to a relevant Silverlight forum discussion thread (I'd recently installed Silverlight v1 in my virtualized Windows machine...as Silverlight v2 is still in beta, I haven't yet gone there). After launching regedit, I navigated to the following key:

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Accepted Documents]

And, after exporting the key as a just-in-case archive, I deleted the following value:

"ag"="application/x-silverlight"

Bingo. The next time I navigated to the webcam address, the login box promptly popped up. And after I entered my access credentials, I was good to go. Some Silverlight forum participants believe that a maximum character count limitation in that particular registry key is the root of the problem. I actually suspect that the specific registry value I deleted is the perpetrator. Regardless, I still seem to have Silverlight capabilities, so I'm not sure what valid function that particular registry value serves.