I'm using SimPE 0.75.69.10, which I think is Chris Hatch's version with the 4gb patch applied.

Occasionally, it just stalls out indefinitely while trying to load a neighbourhood - it tends to get stuck on a random Sim. In this case, I go to File > Exit to close it. When I re-launch, the UI goes missing and I need to use reset layout to get it back.

Does anybody else have this issue?

With my SimPE - not the UC one cuz I don't have UC, I used to get the long pause while it's loading a hood (but from all appearances isn't loading at all, is it?) and I found that if I hit the "start" button down in object workshop and wait for it to load all the maxis stuff first, then go back up to the top and load a hood, then the hood loads up rather quickly.
Try that and see if that helps for you.

Yes, new versions of SimPE take a long time to load. If I switch to another program because I am bored waiting, it never finishes loading and hangs with high CPU usage. If I wait patiently, it will usually finish loading. The toolbars are usually messed up after the hang. I wish the UI layout was fixed of there was a saveable workspace like in Photoshop.

Ah yeah, I noticed alt-tabbing will usually stall it too. I'll try the Object Workshop thing though and see if it helps.

I always set mine to start in local mode (without the file tables loaded). So if I am just looking at a file the program starts very quickly, a couple of seconds. If I want to make CC or browse hoods, I'll go to the preferences and load the file table manually. This seems to work much better for me as normal loading hangs on my elderly computer.

I find that it's necessary to keep hands completely off both keyboard and mouse while SimPE is loading. or it hangs, has to be closed, and when restarted has to have the layout reset. Finicky program! (I have the UC version without the Hatch "naughty" add-ons.)

For what it matters, @Deatherella's tip about the object workshop helps, unless I accidentally alt+tab out.