Thanks, Steve, for your detailed answer.
I understand that solving these issues may take some time.
Hopefully it won’t take so long since we are fully focused on straightening this out once and for all!!!
Vera, I have spent considerable time in different languages , saving and moving phrases to known. The problem seems to exist when the number of saved phrases is large (Russian for me) and not when the number of saved phrases is small, (other languages for me). We are going to find out what the problem is.
Thank you for looking into this. I hope, that you now find a solution. In the afternoon, I’ll check if the same happens in french to me where I have fewer saved phrases.
@alleray - We figured out what was causing the inconsistency in your Known Words totals and just pushed a fix for this error. Now your All Time in the Progress Snapshot correctly matches the number on the left. After correcting these errors, your real Known Words total for Chinese is 1182.
Please let us know if you encounter any more issues with this.
Today I created one LingQ and I deleted this LingQ.
My progress today:
Known Words -2
Created LingQs 1
Learned LingQs 1
The statistics needs to be corrected in some way …
Another point is that my known words went down by about 100 or 200 sometimes in the last days 
Feb. 28, 2011: 5070 known
today 5099 known, but I LingQ-ed in that period about 200 words that were mostly set to known.
Have you moved any Status 4 LingQs to a lower level in the past day? The reason it would show a negative is if you deleted some Status 4 LingQs or downgraded them. Can you confirm what exactly you did?
@alex Maybe. I did some testing, created one LingQ, and deleted it. While doing this I changed the status to some other LingQs. Afterwards I changed the status back to the old value. But maybe I did something wrong or forgot doing sth. Thank you.
Anything’s possible 
If you notice any more possible errors, please let us know. The statistics should all be working properly now, but if you come across anything then let us know so we can finally put this nagging issue to rest.