Adding up columns in TM rarely returns what you might expect for the result. This is unreliable. Furthermore committed memory means slightly different things depending upon the tool you use. It could be the actual commited/charged memory in use or it could include the memory that has been requested but not yet brought into physical memory as it hasn't been referenced yet. Other things that influence this include whether it includes user mode and/or kernel mode and whether it includes shared memory or not. There are lots of articles on the various memory properties and the various ways they could be interpreted.
What it boils down to is if you have a memory leak in the sense that over time your OS has more and more committed memory to the point where Windows can no longer allocate resources. This could easily be caused by kernel software. I recommend you download and run Process Explorer. It allows you to show all the various memory properties including committed memory. Ensure you run it as an admin so you can see all system processes and then order by the committed memory. If a particular process has a leak then it'll work its way to the top over time and you have found your culprit.