I've seen this in the last week or so where PM's I've sent in response to ones I have received just disappear without me deleting them. Is this a known issue/problem with the PM system or do I have a problem on my side?
I've had the exact same thing occur.
I had perhaps 30 PM's in my Inbox and another 20 in my Sent messages folder so I was nowhere near the limit of 100 PM's.
Also if it makes a difference I was and still am using IE7 on XP Pro SP3.
This was a one time isolated occurrence that happened about 2 to 3 months ago where about 15 of my sent items disappeared without me deleting them. Over the intervening time this hasn't reoccurred. My Inbox was totally unaffected.
The one point I noticed was that all of the deleted PM's had been sent to the same person although not *every* PM that I sent to this person had been deleted.
At the time it seemed to me like the person to whom I had sent these PM's had decided to clean up his Inbox and deleting my PM's from his Inbox also deleted them from my Sent Items folder. The nature of which PM's were deleted and which were not seemed to bear this out as well. The PM's not deleted tended to contain useful information regarding subtle aspects of GC2 whereas those PM's that were deleted were more of a chatty nature.
At the time I did not check back with this person to determine whether or not my assumption was correct or not. Also since this issue has not reoccurred (for me at least) in the last few months I assumed it was a one time occurrence and simply ignored it.
[edit] As far as the issue being related to messages I sent in reply to a previous message that did not seem to be case. While most of the messages that were deleted were in fact replies to previously received messages I also had messages where I was the originator of the message deleted as well as messages that were the result of multiple replies that were not deleted. As I said it seemed like it was dependent on useful content since in one case I had the RE:RE:RE reply deleted but not the RE:RE:RE:RE:RE reply of the same PM chain. [/edit]