Tekkit won't work

[Le Fish]

Everytime I try to play Tekkit, it will work for a little while, then this will occur:

Out of memory!

Minecraft has run out of memory.

This could be caused by a bug in the game or by the Java Virtual Machine not being allocated enough memory. If you are playing in a web browser, try downloading the game and playing it offline.

Please help, this happens with normal Minecraft as well. I have tried uninstalling and then reinstalling.

This also shows up while trying to play on any online server.