i need help with firefox, please

[mzsmbs]

i updated my browser to 1.5.0.1 and am having the hardest time to make things work.

i am un able to make .gif to work.

unable to install any extensions etc.

i followed all directions i could find to no avail. whenever i try to install the extensions i get a bar up top that tells me that i need to modify things in the options. well, i allowed things to get installed and still nothing. tools>content>exceptions (the box is checked) i am at a loss.

anybody have a clue? please help. thanks