I dont think it was the reform, but rather the maskilim, I dont remember all the details, but its something like this
A Rav wanted to make a reasonable change to something for a good reason (I forgot exactly what it was though) and he wrote to the Chasam Sofer. It turned out the Maskilim wanted the same change and were lobbying the government to make the change. The Chasam Sofer forbid the change because he felt allowing it would have given the Maskilim a victory on this issue.