You are bugged. This type of bug is caused by extreme lag or sudden ping spiking. This can also be caused when many packets are lost.
To fix this you will either have to close all programmes that use your internet connection eg:"Internet Explorer, Hamachi, Teamspeak, Ventrillo, Firefox, X-fire, Steam and etc.". Once all of these are closed your game should work fine.
If it doesnt.. Make sure you are not connected to any proxy server because proxy servers may cause loads of unwanted ping and packet loss.
If this problem still exists then you may need to get a faster internet connection.
If you already have a good internet connection then please try and re-install SA-MP.
Again, if none of the above work and you have the same problem as moretti when he pings out then you will need a faster/more stable internet connection. If you have a USB modem I would suggest moving to any internet connection that is not wireless.
If none of the above work re-install GTA-SA.
press thanks if this helped you ;D