I was downloading other portal maps and when i started to play them, i realized that my aiming cursor had disappeared. i thought at first that it was just something in the map that made it harder but realized when i went back to play a normal map that it had completely gone!!!

If anyone of you intelligent nice smart people know how i could get it back or even a replacement it would be greatly appreciated

Go into console and type "crosshair 1" to enable your crosshair again.

Some maps enable the console command "Crosshair 0" like The Flash Version Map Pack. (I had problems with those maps.)

Yeah I had this problem to.
One problem can arise by having over 100 maps.