This page covers login problems which fit the following descriptions:
One possibility is that your inventory cache has become corrupted. If this is the case, then deleting it should solve the problem once and for all - assuming it doesn't become corrupted again at some future date.
If your issue was a case of a corrupt inventory cache, then subsequent log ins should work normally. If however, your next log in fails as before, then your will need to locate the problem item in your inventory and eliminate it. So try the solutions described below, one at a time, until (hopeffuly) one of them fixes the problem.
This can be caused by an issue called having a “flat inventory.” If you have folders with a lot of items in them, the viewer can stall trying to create the “inventory view” (inventory folder structure in memory). The solution is simple, but tedious: you will have to create more folders (or subfolders) and sort your inventory such that no one folder has too many items in it. Ideally, aim for under 1000 items per folder.
Alternatively, because this is not a viewer-specific problem, Linden Lab can also help you de-flatten your inventory if you file a support ticket with them. Just make sure to log in on the official Second Life viewer twice (once to fill the inventory cache and a second time to confirm that you're experiencing the issue on their viewer) before contacting Linden Lab.
If you use Vintage Skin (default when logging in using “Phoenix Mode”), the “too many items in single folders” problem may be more likely to occur than when using other viewer skins. This is thought to be because the inventory structure in this skin is slightly different from that of the other skins. Try changing your viewer skin to Latency, which shares Vintage's V1-style appearance but does not increase your likelihood of having this issue, or any of our other skin options. Do this in Preferences → Skins. Change to Latency or another option and relog.
There have been cases where people have ended up with a mass of duplicated calling cards in inventory, so many that they end up preventing successful log in. So try the following:
Hopefully, this will solve the problem. If not, then read the next section.
Should the above method not give a permanent fix, then you should try to deactivate all your active gestures. Yes, all of them. At the bottom of the Inventory window, click the gear icon, and select Show Filters. Click the None button, then check Gestures. Then type (Active) in the search field at the top of the Inventory window.
The above will list all your currently active gestures. Select them, then right click and select Deactivate. Double check that all gestures are deactivated by bringing up the gesture picker at the bottom of the screen; it should show none active.
Now relog and see if you still have issues logging in.
If this solves the problem, the next step is trying to find the bad gesture(s). The best way to do this is with a “divide and conquer” approach. It is not difficult, but it can be long and tedious, depending on how many active gestures you had. Using filters to show only gestures will make this somewhat easier.
One final rare case is similar to the above but involves landmarks rather than gestures.
In this case, it is recommended that you box up all of your landmarks, then delete the originals from inventory, then empty trash (saving the boxed copies). See if this allows for a normal login.
If so, then you can use the “divide and conquer” method above to find the problem landmark(s).