I've often had difficulty with items already in my possession to update properly. Generally I link it to a second account, camp all the way out of the game, and then have it relinked back to me, and this sometimes helps, but not always.
In general, loot you sse on a corpse or freshly linked to you, will result in update within a minute to several depending on server timing. If you see in the Item Collector log, Item #xxxxx updated, and Server Requested Item #xxxxx, then it should be updated very quickly on Lucy's site. Allakhazam's site, can be much much slower (upto an hour very rarely).
The problem I've had with items already in my possession, is the first time I get the updated message, but hte server never requests the item for update there.
Another solution is to find someone else who is running Item Collector and linking the item to the them. There a couple of serverwide channels that often have someone monitoring them with IC running. The tradeskill one, but I don't remember the name atm, and the serverwide.sk:sk also usually has someone with IC running monitoring it. Generally there is at least one trader in the bazaar on each server running IC as well, so /ooc-ing it in the bazaar may get it uploaded.
I've got theories on why this occurs, but won't spout them off, since I have no supporting evidence, and don't know the exact details of the program.
Hope this helps some,
Yther Ore.