simple answer is not to load jquery again in your plugin since it is already loaded by the Elgg core

Yeah, but this doesn't work actually. In such case neither my plugin works, nor the jquery used for the site. I can only get one or the other working, I tried everything. I think new elgg is extremely ful of bugs. It crashes, it's not compatible, it gives strange errors. Any other ideas, please?

There have been no reports of jquery not working in 1.7, so I'm guessing you're using incompatible plugins.  Disable all 3rd party plugins and see if that helps.

I don't have any 3rd party plugins except from modified customdashboard plugin. I just added Jquery support and implemented some google maps within the dashboard using this plugin.

@Vafello - disable all 3rd party plugins. make sure you have the original 1.7 code. if you have problems with jQuery, that is an issue. then report back

I have the original 1.7 with one third party plugin - customdashboard. When i disable it the site works fine, but without it I cannot put my google maps on dashboard which I really need. it worked with 1.6.1. Maybe customdashboard doesnt support 1.7, but it is one of the simpliest plugins, it just overrides dashboard with editable clear space. I tried to declare jquery both in core and plugin, plugin only, and finally core only and none seem to work.

not familiar with customdashboard - can you link to it?

Sure - http://community.elgg.org/pg/plugins/wutaide/read/384314/custom-dashboard-plugin

It's based on customindex plugin I think.

There is nothing in that plugin that would break jQuery so it must be in your modifications.

Well, it was working with Elgg 1.6, so I think this is an issue with 1.7.