There was some offending transaction hanging.
Apparently it was DTSDesigner, LastBatch: today at 6:07 AM
SPID: 54. I killed it and Current Activity can be accessed now.
It actually was causing more problems than I thought.
TRUNCATE TABLE didn't work.
Now it's fixed.
SP_WHO2 question
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How do I find exactly which spid I need to kill?
I look at sp_who2 results - CPUtime,Login,Command, Status
but it's never clear which one is causing the problem.