Rated 5 out of 5 stars

Sometimes I get this error:
The session/window data is corrupted:
undefined(undefined)

undefined:undefined

After it happens all subsequent autosaves fail similarly.

[edit] I'm lucky. I just got this error:
This operation failed due to a file access error:
Component returned failure code: 0x8007000e (NS_ERROR_OUT_OF_MEMORY) [nsIScriptableUnicodeConverter.convertToInputStream](NS_ERROR_OUT_OF_MEMORY)

backup.session

JS frame :: chrome://sessionmanager/content/modules/session_file_io.jsm :: Private.writeFileNext :: line 1796
JS frame :: chrome://sessionmanager/content/modules/session_file_io.jsm :: Private.writeFile :: line 1770
JS frame :: chrome://sessionmanager/content/modules/session_file_io.jsm :: Private.backupCurrentSession :: line 1335
JS frame :: chrome://sessionmanager/content/modules/session_file_io.jsm :: this.SessionIo.backupCurrentSession :: line 154
JS frame :: chrome://sessionmanager/content/modules/session_manager.jsm :: Private.observe :: line 372
native frame :: <unknown filename> :: <TOP_LEVEL> :: line 0

Unlike the one mentioned before, It doesn't cause errors in subsequent saves.

FF messed up (escaped) some symbols when copying from error boxes.
FF ESR 31.4.0

This review is for a previous version of the add-on (0.8.1.6.1-signed). 

Rated 5 out of 5 stars

Sometimes I get this error:
The session/window data is corrupted:
undefined(undefined)

undefined:undefined

After it happens all subsequent autosaves fail similarly.
FF ESR 31.4.0

This review is for a previous version of the add-on (0.8.1.6.1-signed).