Default Memory deficit pop up

Hi folks,

Lately there's been some bothering thing on my HTC Diamond. It keeps telling me that there's too little memory and that i should end some applications, yet i have nothing going on at that very moment. It's not the ROM problem, since it started happening long time after i flashed the ROM (to Gen.Y R5, i believe).

I tried searching the forums for an answer, but I haven't found any. I did install 3D-Anti-terrorist, though, maybe it's the very same virus, but I haven't started calling foreign numbers.

Thanks in advance

Simon