if you have an error "<name> addon tried to call RegisterForSave ..." go to the addon folder /WoW/Interface/AddOns/<Addon name> and open all .lua files one-by-one.
In every lua file do the search for RegisterForSave, if you find the line with this phrase, comment it out, that is done by placing -- infront of the line, so basically if you have RegisterForSave(blah); change it to --RegisterForSave(blah); and also write down the variable for save, in this case blah.
After you went through al the lua files and commented out RegisterForSave(blah); you should have the list of 1 or more veriable, like blah. You will need to do the following to have addon save them over sessions as it used to:
in addon folder there should be a file called <addon name>.toc, open it with editor.
You should see something like:
## Title: Addon
## Interface: 10900
## Author: Me
## URL:
http://www.wowwiki.com
## Version: 1.0
## DefaultState: enabled
## Notes: <Some note>
## SavedVariables: <Some variable>
## OptionalDeps:
## Dependencies:
you are interested in the line that starts with
## SavedVariables:. If the line is not there, insert it somewhere after
## Title: Addon and before
## Dependencies:
Now, add to the end of this line the list of variables you got from the .lua files, for example:
if you had 2 variables:
blah1 and
blah2 and line in .toc file looked like
## SavedVariables: blah your line should look like:
## SavedVariables: blah, blah1, blah2
that should fix it properly, however fix suggested above will still work, somewhat.