Can you please check the error console? do you see errors like those ones?
Error: uncaught exception: [Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIDownloadManager.pauseDownload]" nsresult: "0x80004005 (NS_ERROR_FAILURE)" location: "JS frame :: chrome://mozapps/content/downloads/downloads.js :: pauseDownload :: line 186" data: no]
Error: uncaught exception: [Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIDownloadManager.cancelDownload]" nsresult: "0x80004005 (NS_ERROR_FAILURE)" location: "JS frame :: chrome://mozapps/content/downloads/downloads.js :: cancelDownload :: line 169" data: no]
Can you please check the error console? do you see errors like those ones?
Error: uncaught exception: [Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIDownloadMan ager.pauseDownl oad]" nsresult: "0x80004005 (NS_ERROR_FAILURE)" location: "JS frame :: chrome: //mozapps/ content/ downloads/ downloads. js :: pauseDownload :: line 186" data: no]
Error: uncaught exception: [Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIDownloadMan ager.cancelDown load]" nsresult: "0x80004005 (NS_ERROR_FAILURE)" location: "JS frame :: chrome: //mozapps/ content/ downloads/ downloads. js :: cancelDownload :: line 169" data: no]