How to prevent unwanted window resizing ?

[StuRat]

My windows often resize when I don't want them to. I suspect my highly sensitive mouse is clicking or double clicking when I don't intend to (I could get a less sensitive mouse, but then my fingertip gets sore). The Firefox window often resizes to fill only the top half of the screen, as if the on-screen keyboard had been popped-up (it hasn't). At other times, it seems to maximize. I don't want it to do either of these things. I only want it to resize when I drag an edge. Any ideas ?

Full info:

System: Host: OptiPlex-7010 Kernel: 3.16.0-38-generic x86_64 (64 bit, gcc: 4.8.2)
Desktop: Cinnamon 2.6.13 Distro: Linux Mint 17.2 Rafaela
Machine: System: Dell product: OptiPlex 7010 version: 01
Mobo: Dell model: 0YXT71 version: A02 Bios: Dell version: A17 date: 12/23/2013
CPU: Quad core Intel Core i5-3470 CPU (-MCP-) cache: 6144 KB flags: (lm nx sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx) bmips: 25542.4
Clock Speeds: 1: 1666.125 MHz 2: 1635.500 MHz 3: 1733.125 MHz 4: 1659.375 MHz
Graphics: Card: Advanced Micro Devices [AMD/ATI] RV710/M92 [Mobility Radeon HD 4350/4550] bus-ID: 01:00.0
X.Org: 1.15.1 drivers: ati,radeon (unloaded: fbdev,vesa) Resolution: 1280x1024@60.0hz
GLX Renderer: Gallium 0.4 on AMD RV710 GLX Version: 3.0 Mesa 10.1.3 Direct Rendering: Yes
Audio: Card-1: Intel 7 Series/C210 Series Family High Definition Audio Controller driver: snd_hda_intel bus-ID: 00:1b.0
Card-2: Advanced Micro Devices [AMD/ATI] RV710/730 HDMI Audio [Radeon HD 4000 series]
driver: snd_hda_intel bus-ID: 01:00.1
Sound: Advanced Linux Sound Architecture ver: k3.16.0-38-generic
Network: Card: Intel 82579LM Gigabit Network Connection driver: e1000e ver: 2.3.2-k port: f020 bus-ID: 00:19.0
IF: eth0 state: up speed: 100 Mbps duplex: full mac: <filter>
Drives: HDD Total Size: 282.2GB (3.4% used) 1: id: /dev/sda model: WDC_WD2500JD size: 250.0GB
2: USB id: /dev/sdb model: Flash_Disk size: 32.2GB
Partition: ID: / size: 214G used: 7.3G (4%) fs: ext4 ID: /boot size: 236M used: 46M (21%) fs: ext2
ID: swap-1 size: 17.13GB used: 0.00GB (0%) fs: swap
RAID: No RAID devices detected - /proc/mdstat and md_mod kernel raid module present
Sensors: System Temperatures: cpu: 29.8C mobo: 27.8C gpu: 52.5
Fan Speeds (in rpm): cpu: N/A
Info: Processes: 188 Uptime: 2 days Memory: 4122.1/16003.8MB Runlevel: 2 Gcc sys: 4.8.4
Client: Shell (bash 4.3.11) inxi: 1.9.17

RAM: 16GB (4GB DDR3 x 4) - speed:1600