I'm not qualified to answer most ShareAza questions due to having minimal experience with the program.

Things I can suggest are:
1. Try to ensure your ShareAza program is neither firewalled via your software firewall or via your router. If your router is the issue either enabling UPnP or far better still, port forwarding your router (much more reliable) for the ports ShareAza uses will better help ensure incoming messages are not blocked.
2. Try to vary your search terms. Sometimes searching the same term over and over repeatedly will result in less results due to ultrapeers beginning to consider the term some kind of spam term. You could perhaps experiment with switching artist for song title or album or vice-versa, or combine them, etc.
3. Go to the hosts connection window & remove one host from each network. Bringing in new ultrapeers/super-nodes might help expand the search distance into a new area and potentially rid of dud-nodes.
4. File-sharers only tend to have a limited number of upload slots. If the host's upload slots are all full and their maximum upload queue is surpassed, then download attempts will fail. Almost as though the host was no longer online.
5. Due to the way the gnutella network (G1 & probably G2) works, shared files can linger as being available a notable amount of time after a host has logged off the network. This is generally due to ultrapeers/nodes maintaining references to the data.
6. Some hosts on networks have their program set to share what they download but (possibly due to ignorance) ... this brings in Two types of creeps: (i) Those that remove files from shares during their session on the network(s); (ii) Those that have their upload slots or upload bandwidth set to zero or minimal.
7. Check the hosts from search results and try not to download more than one or two files simultaneously from the same host. Many programs will temporarily auto-block (usually for an hour) hosts attempting to download dozens of files at one time and consider them as greedy hosts. Some sharers have busy upload slots or only one or two set, so attempting to download more than this may result in them failing.
8. Further specific ShareAza advice can be obtained via Shareaza Forums SourceForge Index page

Edit: * If ShareAza users are going to use G1, they should also allocate sufficient bandwidth to share files on the G1 network. ShareAza users have a tendency to use all their bandwidth for other networks. It's been many, many years since I've come across a ShareAza user I was able to download at a rate of greater than 1 KB/s such as 50+ KB/s, instead of 0.1 to 0.5 KB/s.