Losing PR on internal pages only

[Anat]

I'm not even sure when did this happen, but I just noticed that one of my sites shows PR0 for all internal pages. The homepage is still showing PR5.

When I search for site: or allinurl: I only get one internal page as the result... as far as I can see that page is the only one showing up in the serp's as well (it being the links page of all pages :s).

Very strange that this should happen to this site. Do you think it could be temporary? I only just noticed it today (I have over 100 sites atm, so don't look after each one every day). This is a small pet niche site, with about 15 pages of original content. All static pages. Nothing spammy.

Any ideas?