Returning to editing after a long break, and am having a recurring problem here when trying to apply either L&L X or Frames to any clip on my FCP 6.0.6 timeline. However and whichever I apply to any clip, the plug-in doubles the speed of the resultant clip once rendered. The clip appears the same length on the time line, but when I play it back it does so at twice normal speed for the first 50% of the clip, then just black. I recall having this problem some time back, but don't think I ever resolved it.
I'm working on an early Mac Pro, 2 x 2.66Ghz Dual-Core, 6Gb, ATI Radeon HD 3870, OS 10.5.8. Also have a Matrox MXO2 box, though disabled external video when applying L&L after previous issues.
Lock & Load and most other filter effects just render from the input image to the output image which are provided by FCP. If a problem like yours occurs, it's likely a confusion within FCP, maybe due to data corruption.
I'd suggest the following: Close your project, quit FCP, and relaunch. Then create a new project, add clip(s), and apply Lock & Load and other filters. If the problem has disappeared now, your other project was probably corrupted.
If the problem persists, please try to reset FCP's preferences: Quit FCP, remove the preferences file, and relaunch FCP. Check your project. Does it work now?