Is it possible that database is set to auto-grow and it was expanding at that moment?

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>Our imaging database decided to stop taking data yesterday.
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>INSERT statements (run directly from Query Analyzer on the server itself) run and run and never complete (I assume that is because Query Analyzer just doesn't have a default timeout set).
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>We can run SELECT statements on the same tables that disallow INSERTS.
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>We can run UPDATE statement on the same tables that disallow INSERTS.
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>Two tables in the database DO allow INSERTs. I have no idea why.
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>We rebooted the SQL Server machine. No effect.
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>Great. Now I just found out that after a loooooong time (like 20 minutes), INSERTs went through, and now all the tables are accepting INSERTs (at least from Query Analyzer). Is this some sort of crazy locking issue? What sp_ magic can I use to see what is going on? Has anyone else seen this type of INSERT slowdown?
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>I appreciate any thoughts on this matter.
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>Thanks!
>JoeK