While your fonts work well with all of the other softwares, sometimes (on Tiger) word, excel and powerpoint 2004 tells you that all of your fonts are corrupted.
I almost found the solution in French here :
1 – So, just restart your compurer and keep pushed the “Shift” key. You’ll start Mac OS 10.4 in a securised mode (no drivers, no preloaded softwares…).
2- Then empty you bin garbage.
3- Start Word, Excel and Powerpoint
After that, I didn’t encounter the problem any more.