EventSequence in Trace using profiler
According to Importance of the Trace Event Sequence Column and SQL Server 2005 SP2 Changes


  SQL Server 2005 shipped with an Event Sequence stored in a LONG.
  [The MSFT] Support has seen a few traces where the bounds of the signed long are
  exceeded and the Event Sequence becomes negative.


Event Sequence in SQL Server 2005 counts up from 0 to the max of bigint long, and then down from there to 0 again.

"Step 1:  Count up from 0 to 0x7FFFFFFFF
Step 2:  Count down from 0x7FFFFFFF to 0

Start at step 1 again."



  SQL Server 2005 SP2 expands the column to a LONGLONG (signed 64 bit
  integer)


So I guess you're currently in step 2.