Buggy pan controls when the frame rate is slow

[GoogleCodeExporter]

What steps will reproduce the problem?
1. launch webglearth on a relatively slow device (mine is a core 2 duo laptop 
with a radeon X1300 graphics card, 4 go RAM, windows XP 32 bit)
2. Try to pan to move the globe to a specific location.
3. It is very hard and you often reach the south or north pole : 
http://www.webglearth.com/#zoom=3.00;long=-73.82892;lat=-85.71429

What is the expected output? What do you see instead?
To be able to pan correctly

What version of the product are you using? On what operating system?
current beta on http://www.webglearth.com

Please provide any additional information below.
It seems that webglearth does not handle properly mouse button pressed and 
released event. The pan control is still active when you have already released 
the mouse button.

Original issue reported on code.google.com by [email protected] on 20 Jan 2011 at 5:56

[GoogleCodeExporter]

Tested under firefox beta 9

This issue is far less present when the frame rate is faster. 

Original comment by [email protected] on 20 Jan 2011 at 5:57