what could cause inserts getting queued up and db locking??

Background Info:

I have a table with a approx 2.5 million rows.  The table often gets 200-300 inserts per second.  We are see that the
database(7.4.1 Red Hat Enterprise ED 4 way Xeon) will periodically lock up all of a sudden and force the database to
queueup hundreds of queries.  The database comes to complete halt until eventually it clears itself out.  There is
otherdatabase activity going on but the above activity represents 75% of the frequency of the queries.  The table
describedabove has few reads as we try to restrict reads.  We have it set so it does one read every 20 seconds
collectingall of the newest data in the last 20 seconds and moves it to a reporting table.   

What could cause the database to lock up and queue up all the queries?