Straight from the AVAST forums...
DCOM (Distributed Component Object Model) is a set of Microsoft concepts and program interfaces in which client program objects can request services from server program objects on other computers in a network. DCOM is based on the Component Object Model (COM), which provides a set of interfaces allowing clients and servers to communicate within the same computer (that is running Windows 95 or a later version).
For example, you can create a page for a Web site that contains a script or program that can be processed (before being sent to a requesting user) not on the Web site server but on another, more specialized server in the network. Using DCOM interfaces, the Web server site program (now acting as a client object) can forward a Remote Procedure Call (RPC) to the specialized server object, which provides the necessary processing and returns the result to the Web server site. It passes the result on to the Web page viewer.
DCOM can also work on a network within an enterprise or on other networks besides the public Internet. It uses TCP/IP and Hypertext Transfer Protocol. DCOM comes as part of the Windows operating systems. DCOM is or soon will be available on all major UNIX platforms and on IBM's large server products. DCOM replaces OLE Remote Automation.
DCOM is generally equivalent to the Common Object Request Broker Architecture (CORBA) in terms of providing a set of distributed services. DCOM is Microsoft's approach to a network-wide environment for program and data objects. CORBA is sponsored by the rest of the information technology industry under the auspices of the Object Management Group (OMG).
In computing, an exploit is an attack on a computer system, especially one that takes advantage of a particular vulnerability that the system offers to intruders. Used as a verb, the term refers to the act of successfully making such an attack.
Many crackers (or hackers, if you prefer that term) take pride in keeping tabs of such exploits and post their exploits (and discovered vulnerabilities) on a Web site to share with others.
Where an exploit takes advantage of a weakness in an operating system or vended application program, the owners of the system or application issue a "fix" or patch in response. Users of the system or application are responsible for obtaining the patch, which can usually be downloaded from the Web. Failure to install a patch for a given problem exposes the user to a security breach. (However, it can be difficult to keep up with all the required patches.)
Update Windows if you haven't already and keep Avast up-to-date. You'll be fine.. these things are being blocked. :-)