Not sure exactly why this message is coming up as I've never seen nor heard of it before. I did some searching online and found that a possible cause may be corrupt data in your QuickBooks file. Here are a few of the links I found:
http://community.intuit.com/posts/multiple-users-name-list-messages
http://community.intuit.com/posts/can-you-disable-list-data-has-changed-warning
http://community.intuit.com/posts/list-data-has-changed
http://community.intuit.com/posts/list-data-has-changed-2
http://www.softwareshelf.ca/022-Quickbooks-Other.File.Repair.asp
The first one mentions this happens when one user is in AR and another in AP. Not sure if this is what you're experiencing as well but it's worth looking into.
1) That's very strange as Method is no longer requesting data so therefor should not be "locking" these records. I received the screenshot from Ben and if infact the records are being locked as you described, then that message is very misleading. It's just a notification adivising that a change has been made and to see if the screen you're working on has changed.
2) From my research it doesn't seem to be specific to users accessing the same record, the message can display if completely different records are being accessed.
3) Are the you using an Accountant's Copy? Users should see (Accountant's Changes Pending) next to the company file name on the QuickBooks application header, click here to see what I'm talking about. If so then I'm wondering if this has anything to do with it. I created an Accountants Copy, then switched back to Multi-User mode and received this message. I wouldn't think it would restrict adding/editing Customer records but if this is the case then you can try selecting the option to remove this restriction. You'll need to click File > Accountant's Copy > Remove Restrictions... Take heed of the warning as it will make for a lot of manual work on your part, as the changes to the Accountant's Copy will not update the main company file users are accessing. I personally wouldn't suggest this option unless you have no other choice, but prior to making a decision, I recommend you speak with a QuickBooks ProAdvisor/Method Solution Provider as they may know of a better solution.
4) By profiles I'm assuming you mean Customer records correct? Not sure why only these types of records are being "locked". It really doesn't make sense especially when Method is not connected and syncing. Does the file return to normal after you close and re-open QB?
Additionally, did Ben happen to check out the main syncing computers resources being used? It would be helpful to know what his findings are. Especially when Method is running vs when only QB is running.
- Ashur