Mine is a no-intro, clean rom as well. For me, I played through the entire beginning set of 10 courses, filled in my score information, and then it hung on a "saving" screen for awhile before flashing a "save failed" message. I tried a few more things in game to get the save to happen again and every time it flashed to the "save failed" message. Upon turning the GBA off, the EZ Flash IV looked like it was backing up the save file, but of course upon launching the game again there was no high score or other information saved (all 9 of the levels beyond the very first were not unlocked in the practice mode area).
I will note, mine is a USA version rom however, not a European one like you noted. I can try the European one to see if that makes a difference, I guess.