When you finish the test, do you go over the questions you've got wrong? The software on the CD will show you the right answer, together with a detailed explaination. Knowing you've got 67% the first time round is a good start, but unless you know which questions you got wrong, and why you got them wrong, it's hard to improve.
Apart from that, I agree with other posters - take a break. I had a very similar experience this week. I started off with a frame of Performance - two chapters on take-off performance. The material wasn't difficult, and was surprisingly interesting. I read both chapters pretty quickly, made some notes and felt confident. Then I started reading the next frame, which was Operational Procedures. Completely different - thoroughly boring, huge tables of meaningless numbers to learn. I sat there for hours, staring at the pages and not taking anything in. Eventually, I gave up on Ops Procs and went back to Performance. Did the test on the CD for the chapters I'd just read. But I was still so frustrated about the Ops Procs that I just couldn't concentrate on the test. I actually gave up half way through. Next day, I came up with a plan for re-reading and learning the Ops Procs stuff. By Friday, I'd finished reading the Ops Procs material. Yesterday, I did the tests for both frames. Got 80%+ for both of them first time around, and 98% once I'd gone over the questions I got wrong.
Once your brain decides it's had enough, there's no point carrying on. Leave it for a day or two, and it will make much more sense when you come back to it.
FFF
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