If you get "Entry Point Not Found" error messages when starting AbiWord, you are using a different AbiWord.exe than that required by the plugins you have installed. Usually this means you installed a newer version of AbiWord on top of an older release and did not update the plugins at the same time.
You will need to either restore the prior AbiWord.exe or more realistically remove the old plugins (see plugin\ subdirectory, probably \Program Files\AbiSuite\AbiWord\Plugins\, easiest way is to simply delete the whole directory, though you should use the Windows Control Panel Add/Remove Programs function if they show up there). Once the old plugins have been removed, simply download the matching plugins for the version of AbiWord you are running and install them.
The dialog presenting this message is generated by Windows and not AbiWord. Another common cause is the installation of the glib based plugins without installing the the glib DLLs. Should this occur simply rerun the installer selecting install glib (which will download and install the necessary dlls) or manually download glib ( see http://www.gimp.org/windows ) and place in the AbiWord\bin subdirectory.