Cannot be invited into group nor can invite anyone

i dunno if i should put this in bug report but if any of u guys have experienced this and find solution kindly share with me and lightened me off from posting it up as bug..

The Problem: just happened today after i used the LFG tool..after being matched with couples of *uncomplete group and after leaving the last *uncomplete group..i noticed that i can't be invited into random quest-progressing group (the message say im already in a group) nor i can invite others (it say im not party leader) in truth im not grouping with anyone..have try relogin..even exit game for like 10 minutes..but when log back still happening..any helps?

*uncomplete = not enough members

(if i should post in bug report pls tell me so)