Some of these are likely already mentioned, but I can't be bothered to read through 1,000+ pages, sooo... ^^; My apologies for mentioning any of the same things as someone else:
--Audition posts that have little to no information. I.E. no lines, no character descriptions, just a very vague "I need a male/female/unique voice for a 'xx' kind of project. Email me!' Please, please read the guidelines for posting a casting call >.<
--Not being considered for a role simply for lack of previous roles. If it's my audition you don't like, that's well and dandy, but I feel that sometimes the more popular folk are cast the most because of their experience. It's difficult to get one's foot in the door if nobody is willing to give one a proper chance-- even if it's as an extra!
--Constantly extended deadlines. I understand when a producer wants a stellar cast, but there comes a time when either he/she should try and make do with what voices there are, or perhaps shelve the production for later instead of pushing it further and further back.
--Making a deadline, then taking AGES to post a cast list with no word as to what is happening. Just keep people informed, it will give everyone some peace of mind.
--Getting a reply such as "I love your audition! I will definitely be casting you!" or something along those lines- and then, when the final cast list is finally posted...the promised role- whatever it may be fore- goes to someone else. Understandably, someone else's audition may have been more ideal. It's just not in good taste to promise a role you may not give.