First try reformating the Memory Stick, cause maybe the homebrew you have is corrupt...This will "clean" and empty out the memory stick, so anything you want to save upload it to your PC desktop beforehand.
Secondly, if you still notice the problem after you have reformated the MS, then yeah...I would best suggest you update to 2.0fw and then downgrage back to 1.50fw with a homebrew called PSPsetX for 2.0fw...safest way there is.