The first one claims that Interplay is in breach of the Fallout MMO agreement for failure to commence full scale development by April 4, 2009 and to secure certain funding for the game. Interplay disputes these claims and still maintains that it has the right to develop Project V13, together with Bulgaria-based Masthead Studios.
http://fallout.wikia.com/wiki/User_blog:Ausir/Bethesda_sues_Interplay,_new_V13_concept_art
The second one, however, is over Interplay's re-releases of original Fallout games, like the Fallout Trilogy pack or various digital distribution sites.
Turns out that, while Interplay was permitted to sell Fallout, Fallout 2 and Fallout Tactics the contract required all advertising, packaging and other promotional material to be sent to Bethesda for approval first, which, according to the lawsuit, was never done regarding neither the Fallout Trilogy pack, nor any of the releases through Good Old Games, Steam and other digital distribution platforms. Bethesda also claims that the name Trilogy constitutes unfair competition, since it suggests that the pack includes Fallout 3.
http://fallout.wikia.com/wiki/User_blog:Ausir/Bethesda_vs._Interplay_-_more_detail
Continued from http://www.gamesas.com/bgsforums/index.php?showtopic=1038411.