Apllications accessing memory space of another

i thought this might be the right board to start a new thread.

my question is regarding some applications that have been intercepted by defense+

valve steam software, for those of you that dont know it is gaming software used for counter stike and other online games, was intercepted accessing memory of the following in quick succession:-

SandboxieDcomLaunch
SandboxieRpcSs
Firefox
Winamp
Cmdagent

i have also observed several other legitimate applications trying to access the memory of Cmdagent

i have recently just reformatted and resintalled windows about 2 weeks ago
i use a limited user account for general use and use Sandboxie/Firefox and NoScript for browsing.

denying these applications seems to affect system performance in no way.

any explanations why one application would need to access the memory of another? more specifically, unrelated applications trying to do so, especially in quick succession?