The problems were, when I tried Imesh, but I clearly tracked them down to cydoor, as they went away, when I deleted Cydoor with adaware. Of course I know, that many other programs use Cydoor. I am by far not the only one who experienced such problems. They seem to be independent from the software Cydoor came with. All such observations have in common, that the trouble doesn´t start immediately. At the beginning the system is completely normal, then starts slowly getting slower and less stable. For me, for example, it took several weeks, to notice, something was wrong. In all cases, the problems went away after deleting Cydoor, but some people had to reformat due to file system errors in system files.
I started monitoring bandwidth after one month or so, and I don´t know, how it behaved before. There was constant background activity around 500 bytes/sec, so, if this was software download, the software must have at least dozens of megabytes of size.

I have to admit, this was with an earlier version of Cydoor. But since they never listed a bug of this kind as fixed, I am sure it is still there.