It is possible to "overload" your computer with CFS2 add-ons. This is only one possible reason for your error and I would heed Rami's advice first.
Whether or not CFS2 is "overloaded" depends upon your computer's operating system and configuration. No one has been able to give me a specific answer as to what these parameters might be. I have found that keeping the OBJECTS_DP folder down to a bare minimum helps this problem on my one-and-a-half year old HP laptop running Vista. Instead of installing all of the weapons that are called for in the readme of a new plane I download, I open up the plane's dp file and insert stock weapons or one of the few that I have installed. While this works for my laptop, your computer's configuration may be limiting you in some other way. I suggest you clean out your install as best you can.
There are a few utilities that can be found in the out-house's downloads section that can help. While I cannot remember the names of these programs I can tell you there is one to clean out unused gauges, another to delete cdp files (I think it is here?), and another to delete filelist files. I am probably forgetting others. I use them all without problems. Just make sure that any required folders that are empty have a "dummy" file in them before using the filelist delete program as I seem to recall it will delete the unused files (at least one of the program's does this).
Even if your problem is caused by an erroneous entry as Rami said, CFS2 will run better if you keep it cleaned up.