I don't have a copy yet (although plan on it) and don't have a pal Wii, but it sounds like it might be a video mode problem. The US version of SSBB had all the video modes on it I believe, Pro Evolution may not. You might need to use VMC (video mode changer) to add PAL support.

Edit
Freeloader might also work, though I've never used that before.

 

Have you tried freeloader?
I've seen reports this works with the US version and I know it works with the JAP version.
The only issue is that it can cause problems if you connect via SCART.

 

why would i want to do the swap trick with freeloader and cost me more money buying it & mess up the lazer trying to do the swaptrick when i have a modded officall wiikey which plays usa games just 2 games had problems with this new video , ssbb & pro evo.
i got ssbb working perfect with no problems or crashes and in full 480p with deflicker on.
just pro didn't work for the time beening.
i have a look on the key.bin subbject