New Sandisk Cruzer Titanium 8GB - Choppy Performance with Freezes in Firefox Portable. Hardware problem?

Hi All!

MAybe this would suit better as a "google is your friend"-question, but since we're all doing the portable thing here I thought maybe some of you could offer an input.

I recently managed to run my old 4GB Sandisc Micro in the washing machine - 60 degrees Celcius, and I thought I was completely ****-ed.
After drynig a couple of hours I managed to get it online and copied everything to another drive.

Since there's good opportunities everywhere if you look hard enough I realized this was a chance for me to "upgrade" to a bigger and faster drive.
I bought myself a SanDisk Cruzer Titanium 8GB (supposedly faster), took away the U3 and transferred all my portable apps, docs, music and so on.
- And that's where you could say that the end of my joy begun.

My problem is that when I'm trying to run stuff from it (e.g. Firefoxportable) I get a very choppy performance. Scrolling a long page makes the page "freeze"/pause before halfway through, and typing stuff lets me type 5-6 letters, freeze, 5-6 letters more. Switching between tabs is thee same - sometimes it works, sometimes it doesn't. Most of the times I get a "stopped responding" message on top of my window.

The only time I actually get it to work is when I run an almost empty stick with only the Portable apps platform (1.5.2) with Firefox Portable (3.5.1)

Anyone have any ideas on where to start looking for a solution? Is it the stick? Is it the computer? I've formatted the stick a few times, I've tried to copy things back and forth, but it ends the same. The funny thing is that my old 4GB SanDisk Micro still works, and it's a lot faster...
-And I'm "lost"...