It seems that there is a bug when you close IGB while a file is caching. If you do this, IGB prevents that file from caching in future IGB sessions.

To reproduce:

1) Select human genome, and zoom into a few gene models.
2) Select "Load Sequence" and then select "Yes" to cache the 2bit file (be ready for next step)
3) Immediately close IGB while the status bar indicates that the file is being cached.
4) Reopen IGB, repeat step 1, and then select "Load Sequence" again.
*Observe: The cache confirmation popup reappears even it the file was supposedly cached last session. Furthermore, the item never appears in the cache tab, and the console reads "WARN c.l.c.d.RemoteFileDiskCacheService - Aborting download since it may already by in progress on another thread"

We believe this may be happening because IGB may be creating a temporary file in the cache while performing the caching, but if IGB closes, the temporary file remains in the cache, so even though the file has not been cached, IGB thinks the file has been cached because of the presence of the temporary file. This issue should be examined for a possible cause and solution.