LL has announced that they will be restarting the Grid from Tuesday through Thursday to update the server software to 1.25.5. This includes a fix for the “crash on attach” bug.
Do check the sim version (via SL menu “Help” > “About Second Life…”) and look for the line that says “Second Life Server 1.25.5.xxxxx” (where xxxxx are numbers). If it says 1.25.4.xxxxx, it’s still on the old code.
Once the sim you’re on has been deployed with 1.25.5.xxxxx, it’s safe to AIR-Rez your Signature gear again. Yay!