GTA:SA
Ive been working for the past few hours and have isolated a solution to make both SAMP and MTA SA work on a fully updated version of GTA SA, this should only be done if you cannot downgrade it e.g have bought it thru steam. so far its been working perfectly and Ive had no issues.
I must admit before i bought the game through steam, i had been using an illegal version, and had a fair few bugs that most people didn't get.
Anyway, the solution to the problem is simple, just copy an original copy of GTA SA's .exe file into the GTA SA folder and then install SAMP and or MTA into that folder, and it works fine.
Note: the latest .exe for mine(the steam version) is named "gta-sa.exe" whereas this particular .exe is named "gta_sa.exe", so it shouldnt need to replace it or anything but i am unsure whether its the same for the non-steam versions.