100D Locks Up Every Few Days

Every three days or so we have an issue where our 100D stops handing out DHCP addresses, so users are not able to get online. The only way to fix this is to hard power cycle. During the time of the issue, when trying to log into the web interface you can get through the authentication and the next page shows an error 500:

The command line interface reacts very minimally, but I was able to get the process list while this is occurring. Some of the processes are labeled "D". I wasn't able to find documentation for this, but it may refer to dead?

2U, 0N, 0S, 98I; 3954T, 1458F, 323KF
       ipsengine 120 S < 3.5 2.6
       ipsengine 118 S < 3.3 2.6
       ipsengine 117 S < 2.1 2.5
       ipsengine 119 S < 1.1 2.6
       scanunitd 8779 S < 0.7 0.3
         src-vis 92 S 0.3 1.1
       scanunitd 8731 S < 0.3 0.3
         updated 86 S 0.1 1.5
     proxyworker 88 S 0.1 1.1
     proxyworker 89 S 0.1 1.1
          newcli 8780 R 0.1 0.4
         reportd 82 D 0.0 2.0
             dsd 113 D 0.0 1.0
         pyfcgid 8629 D 0.0 0.8
          httpsd 8688 D 0.0 0.8
         pyfcgid 8716 D 0.0 0.8
         pyfcgid 8723 D 0.0 0.8
         pyfcgid 8730 D 0.0 0.8
         pyfcgid 8717 D 0.0 0.8
         pyfcgid 8737 D 0.0 0.7

Any input on this issue is appreciated. I've been restarting the firewall nightly, and that seems to keep the issue at bay. We've already done a format and re-install of the OS and also a complete hardware replacement.

Thank you