W2K server winsock resets TCP instead of recovery, why?

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Hi. Below is a dump of network traffic from a server that manages several 100s of parallel permanent TCP connections. Many clients complain that their connection will be dropped too often. This typical dump shows there were some temporary irregularity in the internet for 80 secs or so. But when the client managed to send the ack, W2K reset the connection simply. I don't know why and if that could be prevented. It ouccurs ca. 10 times/hour.
Another issue: I found that some clients' tcpstack sets TOS 0x20 for the whole of the session (as in the dump below). As far as I understand that's for priority messages. I wonder if some "internet booster" apps do that. I think that's a misuse of that flag. Is that fair to normal internet users?
tcpdump:
03:09:16.338014 server > client: P 20362:20399(37) ack 7159 win 16104 (DF)
03:09:16.568828 client > server: . ack 20251 win 7409 <nop,nop,sack sack 1 {20288:20399} > (DF) [tos 0x20]
03:09:16.568859 server > client: P 20251:20288(37) ack 7159 win 16104 (DF)
03:09:16.721871 server > client: P 20399:20436(37) ack 7159 win 16104 (DF)
03:09:16.800446 client > server: . ack 20399 win 8760 (DF) [tos 0x20]
03:09:17.062165 client > server: . ack 20436 win 8723 (DF) [tos 0x20]
03:09:17.154852 server > client: P 20436:20473(37) ack 7159 win 16104 (DF)
03:09:18.012505 server > client: P 20436:20473(37) ack 7159 win 16104 (DF)
03:09:19.762527 server > client: P 20436:20473(37) ack 7159 win 16104 (DF)
03:09:20.467092 server > client: P 20473:20510(37) ack 7159 win 16104 (DF)
03:09:20.675045 server > client: P 20510:20547(37) ack 7159 win 16104 (DF)
03:09:20.899364 server > client: P 20547:20584(37) ack 7159 win 16104 (DF)
03:09:21.043100 server > client: P 20584:20621(37) ack 7159 win 16104 (DF)
03:09:21.043280 server > client: P 20621:20646(25) ack 7159 win 16104 (DF)
03:09:21.236752 server > client: P 20646:21040(394) ack 7159 win 16104 (DF)
03:09:23.262537 server > client: P 20436:21040(604) ack 7159 win 16104 (DF)
03:09:25.876232 server > client: P 21040:21065(25) ack 7159 win 16104 (DF)
03:09:30.262438 server > client: P 20436:21065(629) ack 7159 win 16104 (DF)
03:09:44.262310 server > client: P 20436:21065(629) ack 7159 win 16104 (DF)
03:10:08.080320 server > client: P 21065:21085(20) ack 7159 win 16104 (DF)
03:10:12.058783 server > client: P 21085:21092(7) ack 7159 win 16104 (DF)
03:10:21.835513 client > server: P 7222:7243(21) ack 20473 win 8686 (DF) [tos 0x20]
03:10:21.835545 server > client: R 3713912832:3713912832(0) win 0