Laptop-hotspot works, laptop-router doesn't; how?

[Farid_2]

1/ My laptop connects to internet and gets a ping through wifi to whether my mobile hotspot or different modem or routers in my office, home and other offices.
2/ The internet works fine when it connected to hotspot,
3/ But it's wobbling at best when to a modem!

I cannot get my head around this one. I've tried using a cable, tried different internet services using other devices, changed dns servers and still it persists. How on earth is this possible?

I mean, find the common denominator.. these work fine: laptop--hotspot, other device--router/modem. these don't work fine: laptop--non-hotspot.

 

[Farid_2]

Well, after three weeks of agony I found a solution, since this morning that I posted, I hope it sticks and be final: I enabled Ad-hoc 11n in my wireless adapter's settings.