"Windows cannot find..." my RMVB

[Xevallah]

Windows XP Pro (5.1, build 2600)
BSplayer 137.826
Real Alternative: 1.5
Real Media: 1.0.1.1 (splitter)
Klite Codec 275b

Fresh install of Windows. Now, everytime I open an .rmvb with BSplayer (via windows explorer) I get a popup saying "Windows cannot find "[location of file]". Make sure you typed the name correctly, and then try again. To search for a file, click the Start button, and then click Search." It still plays, but the windows pop up is a bit of an annoyance.

it doesn't appear when I play a .rmvb in Windows Media Player
it doesn't appear when I open any other type of file in BSplayer
it doesn't appear when I open a .rmvb through/via BSplayer. (instead of windows)

I figure it has something to do with a messed up registrey, but I have no idea what I'm talking about.