I arrived at the jefferson memorial to find at first 3 friendly enclave soldiers that had killed all the super mutants. I proceeded and encountered many hostile enclave troops. I killed at least 15-20 by the time I got across the bridge near piratey pete's dock. There were still a ton more popping out all over the place. I quit after that. At first I thought it was mod related, but after I removed all the mods I have installed since the last time I was in this area with no issues (with another character) and still the issue persisted. I'm going to try going without any mods once the game unfreezes as it froze up when I hit the quit button. I will report as to whether or not that fixes it.

Edit:
I wonder if this is part of some late main quest spawn as they seem to be on the path to the memorial coming from the north, and there is just too many of them and it looks too organized to be a random thing. I have never gone further than the waters of life so I don't really know if this is something that happens later on or not.

Update: I tried it without any mods. only the official DLC and it still happened. going to try it without any DLC's

Update: Even with nothing but Fallout 3 esm. the issue still persists. I think I will have to abandon this character. I would still like to know if anyone knows what is going on, and if there is a way to prevent it from occurring again.

man i love killing enclave i wish that happened to me

I have now discovered ALL my save games are affected by this issue! I think I am going to have to transplant all my saves to another holding file and then make a new character and see if it persists.

I moved all saved game files out of the file they were in and into a totally unrelated area, made a new game, and then went to the memorial again. Once again they were there!

I wonder if I am going to have to uninstall and reinstall my whole game?!? Maybe one of the mods I used somehow altered the game in such a way that it affects it outside of when the mod is selected for use. Luckily I have all my mods backed up onto a flash drive. I think I will back up my saves there as well.

After uninstalling and reinstalling fallout and deleting all my old saves I now have discovered that a mod is the issue. Before when I disabled my mods it didn't fix it, but now it does for some odd reason. I narrowed it down to Powered Power Armor.esp so I have determined that it is no longer an issue with the game itself. I am contacting the mod's author to see if he can help. So I have it all pretty much figured out now as far as the cause.