It used to be true, and maybe still is, if you have special characters in your password the Roku won't like it. If your password is anything but letters and/or numbers, you may want to try changing it.
I assume that your pc "serves" these photos with Windows Media Player. I'd start there and make sure that the location of your photos is still correct, then force wmp to recheck that library. I've seen this behavior occur after a Windows update.
If its really important to you to have it as it was then maybe a full factory reset is in order. You'll then have to link to your Roku account again. Something is stuck, and may actually be in your router. Either way you know it stills works.
I've read a few of those complaints here, and since I had helped set up a home network for a neighbor, who has two Roku TVs, I asked if she has had any problems. None. I suspect it is network issue. Either a router setting, or signal quality. Some new source of interference in the vicinity, like a s...