I am having EXACTLY this problem and its been going on for a LONG time. (Memory expands constantly up to about 1.4 G, slowing the graphics as it gets closer to that target, then SL crashes.)
I have updated my graphics driver many times. I upgraded recently from XP to Windows 7. I have used the SecondLife official viewer (just downloaded today) and it loses memory slower than Firestorm and Singularity do, but all three viewers have the same issue.
1) Mesh makes the problem worse (I lose large chunks of memory, as noted by Task Manager)
2) Moving my camera in and out eats a chunk of memory that is not released.
3) Teleporting eats a chunk of memory that is not released.
4) Holding my camera still does not stop the problem
5) Clearing cache does not slow the problem on the next relog.
Sometimes the viewer crashes instantly with no warning. Other times, the viewer freezes and I have to use Task manager to get rid of the screen.
Second Life 3.7.20 (296094) Oct 29 2014 14:05:13 (Second Life Release)
You are at 69.4, 80.9, 50.4 in 0 0 Acajou located at sim10706.agni.lindenlab.com (126.96.36.199:13008)
(global coordinates 198,725.0, 333,649.0, 50.4)
Second Life Server 14.11.07.296624
CPU: Intel® Core2 Quad CPU Q9550 @ 2.83GHz (2833.35 MHz)
Memory: 3071 MB
OS Version: Microsoft Windows 7 32-bit Service Pack 1 (Build 7601)
Graphics Card Vendor: NVIDIA Corporation
Graphics Card: GeForce GTX 650 Ti/PCIe/SSE2
Windows Graphics Driver Version: 9.18.0013.4465
OpenGL Version: 4.4.0 NVIDIA 344.65
libcurl Version: libcurl/7.38.0 OpenSSL/1.0.1h zlib/1.2.8
J2C Decoder Version: KDU v7.0
Audio Driver Version: FMOD Ex 4.44.31
Qt Webkit Version: 4.7.1 (version number hard-coded)
Voice Server Version: Not Connected
Built with MSVC version 1600
Packets Lost: 11/13,049 (0.1%)