I'm not saying this will work, since I don't allow HTML posting to attempt to test, but:
WARNING, if you choose to modify your database directly, it is completely unsupported. Please create a backup before executing any query as if something happens this backup is your ONLY resource of recovery.
Code
UPDATE `ubbt_POSTS`
SET `POST_MARKUP_TYPE` = "html"
WHERE `POST_DEFAULT_BODY` LIKE "%</a>%"

Basically it's looking in POST_DEFAULT_BODY for the </a> HTML tag, and if it's found it switches the post type to HTML. You WILL need to run the post content rebuilder.

I am a Web Development Contractor, I do not work for UBBCentral. I have provided free User to User Support since the beginning of these support forums.
Do you need Forum Install or Upgrade Services?
Forums: A Gardeners Forum, Scouters World
UBB.threads: UBBWiki, UBB Styles, UBB.Sitemaps
Longtime Supporter & Resident Post-A-Holic
VNC Web Services: Code Modifications, Upgrades, Styling, Coding Services, Disaster Recovery, and more!