When you create the trace, don't add ".trc' to the end of the name as sp_trace_create will also add it.
exec sp_trace_create @traceid = @traceid OUTPUT,
@options = 0,
@tracefile = 'C:\Temp\myTraceFile', -- DO NOT ADD .TRC HERE!
@maxfilesize = 10,
@stoptime = 0
SELECT * FROM ::fn_trace_gettable('C:\Temp\myTraceFile.trc', default)
If you have already added it, just amend the filename from "myTraceFile.trc.trc" to "myTraceFile.trc" or you'll only be able to open it using the Profiler GUI and not using fn_trace_gettable.