MOSS: No search database is associated with the search shared application

Problem:
When trying to run Configuration Wizard after hotfix updates, Config Wizard stop at step 8/9 and C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\LOGS\Upgrade.log says:

Upgrading (search) shared database from the searchApplication is null but it should not be.

Unable to locate SearchDatabase for the SharedResourceProvider

Exception thrown was: System.ArgumentNullException: Value cannot be null.
Parameter name: No search database is associated with the search shared application,
at Microsoft.Office.Server.Search.Upgrade.SharedResourceProviderSequence.get_SearchDatabase()
at Microsoft.Office.Server.Search.Upgrade.SharedResourceProviderSequence.AddNextLevelObjects()

Re-run upgrade using stsadm -o upgrade to ensure the search database gets upgraded appropriately

No search database was found, so skip upgrading it

Thoughts:

• Running stsamd-o upgrade -inplace doesn't help, as it just says: Upgrade completed with errors.
• Stopping and starting Office SharePoint Server Search in Central Admin doesn't help.
• In Central Administration > Application Management > Manage this Farm's Shared Services, you might see that Search Database is empty, typing in new search database and re-running the Configuration Wizard doesn't help.
• Central Administration > Application Management > Check Services Enabled in this Farm says: The Search Service is not enabled for SSP . You should assign an indexer and a search database to this SSP.
  

Workaround:
Delete SSP and create a new one.

Solution:
Unknown.

MOSS: Central Admin search pages give Unknown error

Problem:
When going to almost any search related page in Central Admin or SSP you get plain white screen with black text saying: "Unknown error"

Solution:
This one falls probably in the category 'many things can cause this', but in my case I had modified the application.master because of branding.

Luckily in this scenario the Central Admin site is located on a separate application server (indexing), so best solution was to revert the application.master into default OOB version only on that server. No end-users will access sites on that server, so I consider that a safe workaround.

In cases where you really need to modify the application.master, there comes other solutions, such as presented here.