First Thing to Do...
... is to clear your cache. Sometimes that can fix things.
Corrupt Database Variables
You will need to install the Variable Check module or other similar modules (link to module below, also see my post titled 'Unserialized Theme Variables and PHP Warning: array_merge Messages [nid:73]'). Once you have it installed and enabled you can go to the following menu:
Admin -> Reports -> Check System Variables
... or this URL:
I was receiving the following two errors and I thought taht they were related, but I had no idea how to approach solving them. =(
This first error seems happens intermittently when I load a page from a view and appears on the page when loaded and it has also appeared the admin modules page even though I have error displays off.
Notice: unserialize(): Error at offset 541 of 661 bytes in variable_initialize() (line 1174 of /includes/bootstrap.inc).
line 1174 is as follows:
I found the following code to help clean out orphaned actions which seems to have worked for me. If you have the Devel module installed go to :
admin menu -> Home -> Development -> Execute PHP Code
... and then paste in the following code: