this is much common problem than i thought. a lot of people on the internet having this issue. but there is no one apparent solution. some are claiming to fix the problem by changing router setting or replacing router itself, some say that it was their ISP and after some time it's fixed. in my case i recently switched my ISP and at the same time had a issue with my router(now it's fixed). i'm not gonna spend on a new router only to find out that my old router was ok. i had no such issue with my previous ISP. so i can't put my finger on anything. anyone got solution to this?