[Qgis-user] Disappearing points and polygons

[Declan Troy]

I have simple project of 3 layers:

1)  shapefile of ice distribution from the National Ice Center (US)  
in a Polar Stereographic CRS

2) A point layer of bird locations imported as delimited text (lat- 
long WGS84), and

3) A polygon layer in MapInfo tab format (lat-long WGS84) to fill in  
land masses.

All these show up nicely aligned with 'on the fly' CRS transformation.

My problem is as I change the zoom or pan the display to alter the  
portion of the region displayed various points bird locations) appear  
or become invisible. Similarly  polygons in the land layer appear and  
disappear when they should be visible. I don't think there are any  
such quirks on the base (ice) layer. Very challenging to be sure all  
is displayed within the bounds I want to look at.

This is on OS X using either 1.3 on Tiger or 1.4 Snow Leopard.

Is this just a quirk of 'on the fly' transformations or is there  
something simple I can do to be sure all my data is being displayed ?

Thanks, Declan