No glitch.
It's not a permanent status - like tenure. ;-)
As AlwaysQuilting said upthread, you have to always have a minimum of 20 posts within the last 14 days to maintain "regular" status.
If you fall below that, the "regular" will disappear. Post some more and it will be back the morning following the day you hit the 20 mark again. The system updates automatically at 5:30AM PST.
Oh, and posts in the Classified section don't count towards the 20 posts.
Dems the rules. ;-)
The reasoning behind that makes sense. Whatever perks go along with the "regular" status should only be available to those consistently contributing members. And I guess the only to measure that is by posts.