PRS 505 reading non DRM files as restricted

[diongwi]

My PRS 505 is giving me some problems now.It is reading non DRM pdf's (mainly) and a few other formats as restricted,yet they are not(note: it seems to be only on the external cards).I've tried several methods of correcting this problem to no avail.
It seems to have started recently when I replaced a 2 gig sd card with an 8 gig pny card.If I upload the restricted files to resident memory there is no problem or if I put only them on the external card no problem again.

It only seems to happen when I load up the PNY SD card to about 4 gigs (btw I do have the firmware upgrade.).More annoyingly , the file restriction has now jumped to my Produo card as well.The eBook formats are mainly pdf but some lrf seem to get affected.The eBooks themselves are either a few scans I made for myself or some from LULU.com and the file size varies between the affected ebooks.Any Idea's? I'd rather stay with PDF than change formats.