not sure what's going on here...
running 2.0.1.3 for awhile now & it's been running smoothly, i haven't added anything new. today all users are getting this error & it loops [refreshing constantly]! have i been hacked or what?

i've never seen this error nor can i find it anywhere in the lang files to try & figure out the problem...i have 3 other sites [all 2.0.1.3] on the same server that do not have this error showing up, so i'm thinking it's not a server issue. [?]

any help greatly appreciated! thx!