Error #1025 150/152 (no replies)

Hello !
When trying to delete a foreign key from my table MYTABLE, I get this error message: #1025 - Error on rename of '.\mydb\#sql-1de4_60' to '.\mydb\MYTABLE' (errno: 150).
I tried to look up the real foreign key name (using SHOW CREATE TABLE) but nothing helps. I also tried dropping the foreign key and deleting the column, but nothing worked! Any tips? Is this a bug?

Best regards,

MH