This is strange. Viewing the "web console" of the browser when this happens will be likely helpful. The procedure to do this is specific to a given browser and probably version, but if you search on the internet you should be able to find the instructions. Or you can let me know the exact browser and version you are using and I can help. For instance, for firefox, you can click on Tools > Web Developer > Web console, if the proper plugin is installed.
Once you have this, post the contents of web console and we can debug further. Note that you may have to wait for sometime for the console to record the logs - don't immediatey close the browser window...