Welcome to the forum.
Where are you seeing that "flashing," such as when you play the Timeline?
What version of PrE are you using, and what is your OS and its version, i.e. Win7-64?
What are the pixel x pixel dimensions of those JPEG's?
Good luck, and please let us know just a bit more,
Is this one of those "it worked before but not now" problems or rather "it never worked before" type?
Since this is Premiere Elements 9, are you running the 9.0.1 version of it? The information that Hunt is seeking is important for sorting this all out. The answers are in the details. And, we do need more details to sort this out.
If you determine that pixel dimensions oversized for the project are not involved and that an out of date video card driver is also not involved, then we might have to look to deleting the BadDrivers.txt file.
In reflecting further about what you are seeing in the previews....are you looking at a rendered Timeline and would you call what you are seeing more flicker than flashing?
But, first the details.