GPS Visualizer wants header information. It worked the last time I tried without modifying anything. What has changed?
 
Since you say it is nmea data, I tried changing to 20101030133437.nme and 20101030133437.nmea. Neither worked.
My first lines of data from log file:
$GPRMC,133437,A,3036.3121,N,09734.1463,W,085.5,168.2,301010,0,E*73
$GPGGA,133437,A,3036.3121,N,09734.1463,W,1,4,10,,*19
According to the http://www.gpsinformation.org/dale/nmea.htm#RMC, this appears correct. It should be recognized as nmea. I have questioned the http://www.gpsvisualizer.com/map_input?form=googleearth site via the link  let me know.
 

No valid GPS data detected!
If you think you really did upload a valid GPS file, please let me know and I'll look into it.
Often, this error comes up because you  didn't include a header row at the beginning of your tab-delimited or  CSV plain text data.  If there's no header row, the computer has no way  of knowing which numbers are which!  For example, GPS Visualizer has no  idea what this means:
    
        
             45.40252,-121.77589,1399,point 1 
            45.39254,-121.69946,2394,point 2  | 
        
    
Whereas the following makes perfect sense, because there's a header row that defines the fields:
    
        
             latitude,longitude,elevation,name 
            45.40252,-121.77589,1399,point 1 
            45.39254,-121.69946,2394,point 2  | 
        
    
Note that the order of the fields is irrelevant, as long as the header matches what's underneath it.
 
It's also possible that you simply have the wrong suffix on your  file(s).  For instance, files containing comma-separated data should  always end in ".csv"; GPX files should end in ".gpx".
Here's the (almost) complete list of filename endings that GPS Visualizer recognizes: