[Translators] unclear string; synonyms

[Thomas Bellmann]

What is this string supposed to express?:
| #: src/plugins/libravatar/libravatar.c:403
| msgid "Failed to load missing items cache"  

Does it mean
Failed to load the cache named "missing items cache" 
or
Failed to load the missing items from the cache?

Additionally, sometimes the strings referring to libavatar mention
"icons" and "icon cache", sometimes "items" or "item cache". If
these always refer to the same things, identical words should
be used to avoid confusion.
Example copied from de.po:
| #: src/plugins/libravatar/libravatar.c:394
| #, fuzzy
| msgid "Failed to create avatar image cache directory"
| msgstr "Ordner konnte nicht erstellt werden"
|
| #: src/plugins/libravatar/libravatar.c:403
| msgid "Failed to load missing items cache"
| msgstr ""  

Regards
Thomas