yahoo mail not opened in Ubuntu, but opened in Kubuntu

Two years back I installed Ubuntu 12.04, 32 bit in my i3 computer with 1TB Hard Disc & 4GB RAM. After a few days I found that yahoo mail was not get opened, even with Thunderbird it timed out. When Ubuntu 14.04 released, I installed Ubuntu 14.04, 64 bit freshly and the problem persists and as a change I switched over to Kubuntu 14.04, 64 bit and found yahoo mail is get opened easily without any problem. Afterwards I try to open yahoo mail with Ubuntu 14.04, 64 bit Live DVD in try Ubuntu mode and again it not get opened. Now Kubuntu 14.04 is working perfectly in my system, but my query is why this happening? If possible, please explain.