why i cant play some servers

Put the summary of the bug you're having here

*What I expected to happen was that i can play nexus in 1.7.9 and other servers and even my 1.7.10 why cant i play and it is not 1.8 i can play with 1.8

*What actually happened was i keep crashing while trying to play some servers
i cant play almost all minecarft servers

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
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