Not familiar with UOTiara, but this is worth mentioning for a lot of generic loading bars. The loading bars aren't always 100% reflective of the progress as a normal person would interpret them. For example, you may load then 0-95% in like 30 seconds, but then it hangs at like 95% for 3 minutes. Typically that case is due to the loader reading it as something like 47/50 files being done, and the last 5 files are being loaded. What it's not telling you, would be the size of those 47 files could be like 100 kb each while the 3 remaining files are 100,000 kb each. I'm sure that won't make sense to a lot of people, so don't fret if you have trouble grasping what i'm saying.
So it'll tell you 95% done due to reading all those files, but it's not telling you the file size of the remaining files which is the real concern. This can also be why some programs show up as "Not Responding" while loading.