Like more than a few others, I've had a certain issue with my Sprint CDMA Treo 650 that not everybody seems to have.

In this case, the phone seems to reset randomly when Chatter is running, either in the foreground or the background. The problem is pretty quickly reproducible. When I go to the Phone application and dial ##377, I would see errors like this:

A reset was caused on 06-1-3 at 14:55 while running "Web":
MemoryMgr.c, Line:2679, Chunk over-locked
The error message will blame whichever application is in the foreground at the time. If you happen to be browsing the web using Blazer, the reset will be caused while running "Web". If you're using the Phone, the reset will be caused while running "Phone". And, of course, if Chatter is in the foreground, the reset will be caused while running "Chatter".

I had thought that I had clearly identified the problem as Chatter-related, because the error only seemed to occur while Chatter was running, and I had no other interesting 3rd-party applications on my phone. However, this didn't turn out to be relevant. Google around and you'll find numerous cases of people reporting "Chunk over-locked" errors who don't have Chatter installed. The vast majority, if not all of those cases, are resolved by getting replacement hardware.

I was skeptical, myself, because I had thought that it wasn't really the hardware being replaced that did the trick: I'd presumed that what really fixed the problem was getting a completely empty phone. But, if you're having "Chunk over-locked" errors on a Sprint CDMA Treo 650 and want to see what you can do to resolve them, try following the steps I describe below. I've pieced this together from my own experience and from reading various forums online.

1) HotSync, then try a hard reset ("Erase all data? - Yes"). HotSync again to restore everything. See if you can still reproduce the "Chunk over-locked" problem.

2) The problem should reproduce itself even if another app is in the foreground, and even if Chatter is entirely offline. Start Chatter, set all mailboxes to offline mode with no recurring QSync, and then go do something else with the phone. Use one of the 1st-party apps like "Phone" and "Web". Eventually, you should get a "Chunk over-locked" reset, and the ##377 reset application will be the foreground application, not Chatter. (BTW, this is itself some limited evidence that Chatter isn't really to blame.)

3) Buy the $5/mo phone insurance policy, if you haven't already done so. This puts you on a higher support tier for a very minimal fee. (They even make a note of this on your support ticket receipt!)

4) Go to Sprint, show them a "Chunk over-locked" error message in a 1st-party app (Phone or Web) and open a support ticket.

Note: Do not mention Chatter. If they ask if there's a way to reliably reproduce the problem, say that you don't know what exactly reproduces it, but it sometimes happens while you're browsing the Web or using the telephone. (All of this is formally true, if somewhat deceptive by omission.) If you do mention Chatter, they will just tell you that Chatter is to blame and that you should delete Chatter.

The support rep will suggest a hard reset. Helpfully agree to do this. Do not insist that you've already tried it. Leave the store. :-)

5) This time, HotSync again and then try a zero-out reset.

http://kb.palmone.com/SRVS/CGI-BIN/WEBCGI.EXE?New,Kb=PalmSupportKB,ts=Palm_External2001,Case=obj(887)
http://tinyurl.com/5qove

I found the instructions a bit confusing. Here's my way of restating the directions: A zero-out reset requires three steps.
Step 1: press Up and Power simultaneously
Step 2: press HotSync
Step 3: press the reset button on the back of the phone

Use two people to do this. Count "Zero, One, Two, Three". On 1, press Up and Power, on 2, press HotSync, and on 3 press reset.

The instructions claim that the phone should appear dead for a long time, possibly minutes. But don't worry about that; in my case, it was only dead for a few seconds. You'll know you've succeeded if the phone is, by default, making you tap on stylus targets, and did *not* ask you whether or not you wanted to "Erase All Data".

HotSync again to restore all of your apps and data. Again, the problem will reproduce itself.

6) Once again, reproduce the error in a non-Chatter 1st party application and bring the phone back to the store. Talk to a different support rep from yesterday. Show them yesterday's support ticket and today's error message.

They will ask you: "Do you have any third party applications on the phone?" and you will say: "Yes, but last night I tried a hard reset with zero-out, and it still kept happening." (Again, somewhat deceptive by omission, because it kept happening only after restoring your applications.)

The support rep will take your phone and run diagnostic tests on it. The rep told me that this can take 20 minutes, but it may take longer than that.

Some people have reported that their phone passes diagnostic tests at one Sprint store and fails the tests at another location. Go to another Sprint store, explain to them that your phone is still crashing after a hard reset, and have them run the diagnostic tests. They'll very likely replace your phone then.

In my case, they re-emerged in 45 minutes with a replacement phone; I took it home and HotSync'd again to restore all of my data and Chatter. At last, the "Chunk over-locked" errors were over.

Good luck!