thumbnails randomly updating + navigation window missing

Hi,
More issues showing up in my elgg 1.6.1 install :
1/ thumbnails created for groups or uploaded images and shown on the welcome page (custom_index) for example, are randomly showing. it is not a constant issue. Sometime half of them show up, a refresh and then the other thumbnails appear and some that were previously shown disappear... there does not seem to be any logic behind it and I could not replicate the issue on my test server at home. my hosting service seems fairly standard beside the fact the db is not on localhost...
2/ widgets sometime do not get properly populated and I get the message : elgg could not connect to the DB using given credentials. I just go to edit, and save without making any change and woof... the data shows up !
3/ page navigation, or anything showing under the navigation area of the screen (page navigation for example) remains blank. page title is not shown and any sub-page is not accessible, except through direct linkage.
what could this issue be related to ? hosting ? the fact that the db is not on;localhost ? my install is currently hosted by http://www.000webhost.com/
Any  suggestion of hint, solution or explanation would be greatly appreciated !!