This is probably caused by a wrong DMA mask setting. If you changed it when installing PFS2, then change it back. The right setting for the DMA mask is controller specific and is independent of whatever filesystem you are using. However, due to the highly optimised design of PFS2 it is more sensitive to mistakes in the DMAMask setting then FFS is.
Therefore it is possible that PFS2 has problems with a DMAMask setting that you previously had no problems with. If this is the case, then check the manual of your device for information. If this doesn't help, then you can use the guidelines for determining the DMAMask in the manual. Since we don't know the specifics of every device those settings are not always the best.
The manual mentions a setting of 0xFFFFFC for Zorro-II devices on Zorro-III machines (the German manual falsely states 0xFFFFC, see note). This applies only for the very specific case of a board designed for the A2000 used on an A3000 or A4000. And even in that case it is not always necessary. This is the setting that can cause PFS2 to use Chip RAM for its buffers. If you know that FFS or AFS used Fast RAM for its buffers, then so can PFS2: change the DMA Mask.
Almost every other device works with a DMA Mask of 0x7FFFFFFC. This setting allows PFS2 to use any memory.
Note: in the German manual the value '0xFFFFC' is suggested for the Mask on Zorro II machines. This is wrong. The right value to use is '0xFFFFFC'.