Happy New Year Zac.
Was curious if there is any news or status on this? Hope there is good news. 
A DLink rep did ask me to call tech support, but at the time I was travelling, and I had an idea, so not done yet. Tech support, if history tells, will simply want me to do everything I've already tried plus at least one or two impossible things to see if I'm listening (change the band, turn off security, change the clients, upgrade/downgrade device firmware and client drivers, move the thing to the zero room of a TARDIS to avoid local interference, hop about the room on my left leg while holding a client PC so its antennae are exactly 1.5m from the unit's antennae to be sure I'm not out of range, &c) before they will listen to anything I have to say (it's not SCSI, so ritual sacrifices are hopefully less likely). I want to try to have some confidence in what I have found when I do call them.
While I was travelling, I took some 'light reading' with me: In particular my notes about my network and the log files for the past few months. It took some effort to correlate something to the issue, but I have found a suspect change that seems to have caused the problem to surface. I think it is speculative, but the correlation looks high.
Oddly, what I suspect is *not* radio related. Maybe that is good news...? It is something that should be utterly unrelated, IMNSHO, but after nearly five days of testing (I will not believe it until after at least a week), no drops.
About the time the original issues started, I was adding some new devices to my network and reorganised the IP addresses. Seems innocuous enough, and I had done that to a limited degree before, except that I also upgraded my DNS and DHCP server daemons (on my main fileserver, a Linux box) and switched a number of devices to running statically allocated DHCP (MAC to IP mapping set at the DHCP server) instead of locally assigned IP addresses. The idea, of course, is to give me central control of IP addresses not only of PCs but everything. Seemed that if I had to do something like this again it would be easier. Ah, if only...
At that point, I switched almost all of the network devices to DHCP client mode as well. Most of the devices seem to work reasonably well that way. However, a few do not (including the DAP-2590).
Shortly after this change, it seems, the DAP-2590 started issuing the 'Initiate wireless success' messages while dropping all its clients at once. I can't say exactly how long, since I was not having it copy its log entries to another device at this point. However, a couple weeks after the change, I had the DAP-2590 sending its logs to a Linux box. About a couple weeks after that, I decided to change the DHCP renewal interval (I didn't like the amount of clutter in the dynamic space that stuck around after certain changes, so I set it to age entries more quickly). At this point, the DAP-2590 started issuing 'Initiate wireless success' messages and dropping its clients at intervals that were within a minute or so of the new DHCP renew interval.
Not sure why I did not suspect it before... Probably my bias is toward the radio problem by experience (my first DAP-2590 unit) and that combined with the same log message (which looks like a radio-related message to me) attracted that conclusion.
The first couple days after I got back I had the thing running as it was (DHCP client but the server was told to always give it a specific address). It would issue the 'Initiate wireless success' messages and drop clients at about the time it renewed its lease, every 12 hours on my network. Since clocks are hard to synchronise, and distributed logs involve a lag that is particularly noticeable against local frame captures, I can not say the specific order of the DHCP lease renewal versus the 'Initiate wireless success' message versus the client drops, but they always occurred together, and within a few seconds usually of the expected DHCP renewal interval.
Right now, I have the DAP-2590 running firmware '1.25 15:41:33 08/31/2012', with a saved configuration from before I took it down, except that I have set it to use a static IP address instead of running as a DHCP client. It has been up for '4 Days, 19:26:16' and the only 'Initiate wireless success' message came a few moments after it booted, with no client drops during this run (but only one client at this point).
Once it gets to a week, or if it starts dropping again before it gets there, I shall call DLink's tech support and give them a chance to walk me through their process. Maybe it will go better this time? Maybe they can figure this out and resolve this problem in a new firmware version. If it does appear to be related to DHCP client mode, I wonder whether it applies to other devices...
I any case, I would hope they can at least make the log entries more useful in the future (perhaps some indication of *why* it does something in addition to the fact of it doing something).
