Some people have run into a problem uploading mesh. There is a JIRA filed on the problem: SH-3055 –[PUBLIC] Cannot upload any model (*.dae) file; “xxx failed to upload, see the log file for details”.
There is a fix making its way through QA. See the preliminary build in Simon’s repository: 266471. I understand this version has a fix by Runitai Linden. Some other issues in that build have kept it from merging with the Development or Beta braches. Until the other problems are resolved this fix is a bit jammed up.
If you are having mesh upload problem, try the viewer and provide feedback on the JIRA. I can’t tell which JIRA’s are open to basic JIRA users. But, I think this one is open to general users. If not, email Alexa Linden and mention SH-3055.
You probably know viewers can update quickly. The viewer provided above (266471) is linked to via a static link. The newest version from that repo is here: Latest Simon II. I haven’t read the branch notes so I’m not sure the new versions are better for mesh upload. As the Lindens are likely to experiment with adding and removing fixes to find problems you just can’t know without reading the notes. Even then it may be impossible to tell exactly what is going on as these notes are often likely meant only for those making them. But, it may be worth a try.