Well you got me a little further. With a pretty similar result.
" yum install mplayerplug-in-2.75-0.FC3.i386.rpm
Setting up Install Process
Setting up Repo: base
repomd.xml 100% |=========================| 1.1 kB 00:00
Setting up Repo: updates-released
http://fedora-mirror.dkuug.dk/linux/...ta/repomd.xml: [Errno 4] IOError: HTTP Error 404: Not Found
Trying other mirror.
repomd.xml 100% |=========================| 951 B 00:00
Reading repository metadata in from local files
primary.xml.gz 100% |=========================| 797 kB 00:02
MD Read : ################################################## 2623/2623
base : ################################################## 2622/2622
primary.xml.gz 100% |=========================| 214 kB 00:00
MD Read : ################################################## 506/506
updates-re: ################################################## 506/506
Examining mplayerplug-in-2.75-0.FC3.i386.rpm: mplayerplug-in - 2.75-0.FC3.i386
Marking mplayerplug-in-2.75-0.FC3.i386.rpm to be installed
Resolving Dependencies
--> Populating transaction set with selected packages. Please wait.
---> Package mplayerplug-in.i386 0:2.75-0.FC3 set to be installed
--> Running transaction check
--> Processing Dependency: mplayer > 0.90 for package: mplayerplug-in
--> Finished Dependency Resolution
Error: missing dep: mplayer > 0.90 for pkg mplayerplug-in"