Hi hanshans,
This typically occurs when another plugin or theme flushes the redirect rules incorrectly, this should only be done during plugin activation/deactivation.
Please try the following:
1. Deactivate ThirstyAffiliates, don’t worry your links are safely stored in the database.
2. Reactivate ThirstyAffiliates
3. Visit the Settings->Permalinks page and click save (ensure your .htaccess file is writable by the web server).
4. Go back to ThirstyAffiliates->All Affiliate Links and view one of the links, it should be redirecting properly.
Failing this, you can test deactivating your other plugins one by one to see if you can find the conflict.
1. Disable suspect plugin
2. Visit Settings->Permalinks page and click save (ensure your .htaccess file is writable by the web server).
3. Goto ThirstyAffiliates->All Affiliate Links and click view on one of your affiliate links to see if this fixed it.
4. If that didn’t fix it, you can reactivate that plugin and try the next.