The one time use bolts are for 2007+ models (according to BMW mid 2006, but on this forum we've seen cars built december 2006 that still had the old style bolts).
Previously the strut towers had welded in bolts. The only way to retrofit is to break off the mounts and weld in the new style mounts. Instead of doing that I opted for using Nord Locks. My 2004 2.5i Roadster never had a problem either, I imagine that I either drive the M harder or there's something about the older suspension that makes it more prominent.
Definitely torqued to the right amount, I have a Precision Instruments
split beam torque wrench (highly recommended).
Here's a picture of Roffle's (broken) strut mount, notice that it's a regular nut:
Here's a picture of the new style mounts with one time use bolts, courtesy of Ron Stygar:
