Had this issue a while back, so I upped my vram, and the issue was resolved for a while, but now it's back again.  

Vram has been upped as much as it can be.  I'm running an Nvidia GTX 980 Classified Gaming ACX 2.0, i5-4690, 16GB RAM, game settings pretty much maxed out with a good amount of memory still left over.

Any other suggestions on how to remedy this error?

How many game cars have you replaced with mods? I was getting a memory error myself when I replaced too many. There are also situations where certain modded vehicles will cause this issue. I changed police3 back to the original car and no longer got the memory error. Try that. You might also want to look into adding extra vehicle slots. There's a tutorial on it LOCATED HERE. I haven't gotten any memory errors adding vehicles that way.