It was just updated.
There was actually a post a few weeks ago (maybe more) where someone posted a step by step guide to making the Aether work with the most recent version of the Technic Pack (SSP)
OP: Search these forums for that thread as he has a link to the recently updated version. You don't need to use it with the Technic pack, you could just install it to the Vanilla Pack included in the launcher (If you do that you don't need to bother with back patching, just select the Vanilla option for 1.2.5 (NOT 1.3))
That is what I meant. It might be an issue with ID resolver not correctly identifying open ID's or something like that. The reason I asked is because if that is the case, there could be a slew of other errors due to the fact that the devs expected ID resolver to fix the ID's for them and thus there are some more conflicts.
Metadata not found just means that the mod creator did not include a text file that describes what the mod does. It has nothing to do with the functionality of the mod. Are you sure you have the correct bit version of Java?
P.S. Metadata not found means nothing. It is just telling you that the mod author did not include a document with a description of the mod. The mod will still work (if it is loaded correctly)
OP: Try redownloading the pack.
What operating bit do you have? Are you using an Antivirus? Do you have the same bit OS and Java? Have you disable firewalls? Is there an error report? I could go on...
http://www.java.com/en/download/manual.jsp
Choose Windows 64 bit
Also try allocating more memory in the launcher by going into Options and increasing it.