Why did all XP lose access to one of the workgroups?

Question

Computer networks

There is a network of 10 xp and 10 sevens. 6xp are in workgroup 111, 2xp in 222, 2xp in workgroup. 6 sevens in group 111, 4 in 222.
The problem is that ALL XP lost access to working group 222, there is access to other groups. Sevens go everywhere normally.
When you try to log in with XP to group 222, it says - no access to 222, you may not have rights to use this network resource. The specified network name is no longer available.
Everything worked fine yesterday. Reconnecting to different switches had no effect.
Are there options to solve the problem? The installation of the seven is not considered, the computers are 10 years old

Answer 1

No updates or software have been installed in the last 24 hours.
ps The problem has so far been solved by rebooting the switch, but it's still interesting what it was.

Answer 2

forum.ixbt.com/topic.cgi?id=86:17