dxrom, this is a client error not really AUO, we fixed a few things that could aggravate that client situation from AUO's side, users have this issue sometimes using Razor or even plain client.
If that latest build did not worked for you, you can try checking out other explanations for this if you are running windows 7:
"As far as I've read people solved this by:
1) Cleaning up/uninstalling programs, specially if HD it is almost full, disk cleanup and defragmenting;
2) A few have reported that it may be due to spywares, trojans, etc, so, trying to remove those may be a good idea;
3) Others just had a lot of programs running, they closed a few and could launch UO just fine;
4) Some players had to edit their virtual memory paging file size config via Control Panel -> System -> Advanced system settings -> Advanced -> Performance Settings -> Advanced -> Virtual Memory Change -> Custom min/max values (keep in mind these values are in MB);
5) Trying a different client version;
6) Updating your OS."
Please, let me know in case you have this covered.
Thanks for your support using AssistUO!
