Broken +use/build (toggles For Some Reason)

Reverend

I'm finding that my +use key (no matter what it is bound to) is, instead of BUILDING structures, 'toggling,' as if I'm pressing and releasing the key while building. The delay this causes is AMAZING when I don't have my Knife selected as the active weapon, with a HMG active, I may as well be sitting down for all the speed I get building a structure.

This doesn't happen every time, and I can't seem to track down the cause. Any help?