I observe the similar issue. I have two DCS-930L cameras. One works on 1.03 the latter on 1.08 firmware. Web server hangs from time to time on both devices.
Observations
The first sign of web server problem is that there is on image on /image/jpeg.cgi . When opening this URL the information "Web server: no such file" appears. There is also no image on /top.htm page. But the web interface still works for a while. After playing with web interface - switching tabs, refreshing several times - the web server hangs. There is no HTTP response as well as no response to ping. The led is constant red.
The cameras are connected through ethernet wire (no wifi). Disabling motion detection seems to have no effect.
How to fix this issue?
For those suffering from the issue, the solution for restoring the camera web server after the breakdown (provided that camera is connected through the wire):
1. Unplug the ethernet
2. Restart the camera by unplugging the power
3. Wait until camera starts, the red light will be blinking and then change to constant red light
4. Plug in the ethernet coord
Sometimes this steps have to be repeated.