I recently installed Dropbox on my computer.The problem is that when Dropbox is syncing i.e. uploading or downloading no I cannot use internet on my other programs like firefox. On the other hand this does not happen in Linux Mint(Cinnamon) 15 or Windows 8 which is installed on the same computer. Not only this any other computer connected to the same Wifi router, their internet is diabled too. The current system on my computer Kubuntu 13.10 32bit version, I recently upgraded from version 13.04. I asked the support team of Dropbox and this was their reply.
"Hi Mazhar, Thanks for contacting Dropbox. Unfortunately Dropbox can only upload and download as fast as your internet service provider (ISP) allows. Consumer ISP's normally provide 1/10th the upload speed compared to download speed. Normally Dropbox doesn't use all of your bandwidth, just to be polite. However, you can change that by manually setting the upload/download speed:
Right click the Dropbox icon in the system tray at the bottom right of your screen, by the clock on Windows or menu bar at the top of your screen on Linux.
Click on the gear icon in the Notifications panel and select "Preferences" from the menu
Click the "Network" tab
Click Change Settings next to Bandwidth:
Set the Upload and Download to a specific kB/s limit if you know your connection speed or simply Don't Limit to allow Dropbox to use as much bandwidth as possible.
NOTE: Setting your Upload to Don't Limit or a higher number than your connection is capable of will likely cause all other internet activity on your network to slow significantly.
Unfortunately this did not not help.Please solve this problem.