crash by run out of virtual memory

**Enviroment: **online game (32x) OS: win10 DX:dx9

CrashReport (from dump) : run out of virtual memory

Since many of our user’s OS upgraded from win7 to win10 and new art-resources imported to the game, the crash occured to our udk based project.
Many users reported after running a few hours , their gameclient will get crashed at random point.
We get the error D3DERR_OUTOFVIDEOMEMORY after get the return of VerifyD3d9Result,but acturally the user has more memeory avaliable.Sometimes it will happen at the usage of about 2 GB, and sometimes it will be near 3 GB usage.
We happened to decrease some of our texture size from 1024x1024 to 512x512 and the problem disppear for a month,but after importing some new resources(also 512x512) to the game, this crash reoccured .
We doubts the problem may be the support for dx9 by win10 or the resource limitation of udk.
Is there any instruction about this kind of crash problem?

Does running the game from the 64 bit exe does the same? Which game is that and on what version of udk was created on?