There are two things which are a bit off-putting about this.
First, the fact that the same exact type of bug had been known in 1999 and yet they either failed to fix it in the newer code base or they reimplemented the exact same bug in new code.
Second, almost certainly the reason that these bugs weren't caught earlier is because it's unusual for Windows to have such long uptime (50 days for Win 9x is impressive, and over a year for Windows server equally so). More so, almost certainly the average user has such low expectations of windows reliability that if they see the system become unstable or slow after a long period of uptime they will as a rule merely reboot the system rather than investigate.
Edit: a thought occurs to me. Perhaps the "fix" for the older problem was to simply change from using milliseconds since last boot for tcp/ip socket age to using hundredths of a second. I really, really hope that wasn't the case.
