Would be helpful to know what changed so that it is now working. Please advise.
The translation of the messages appears to be (apologies for no Spanish)
"script on this page may be busy, or it may have stopped responding. You can stop the script now, open it in the debugger, or let it continue its execution."
This still indicates to me that it is a server problem. Have you contacted the people who provide your hosting service. Sometimes hosting servers have a lot of people on one machine or limit the band width or have a very small time slot.
Just for clarity does this happen when you are trying to download? Or Upload? Or say just list all categories? Or list all downloads?
Do your downloads have images associated with them? If so what is the original size of the images (width and height in pixels, and also file size)? And how many per download?