Tnx for all the replies, in the meantime i came to the same conclusion that it must be the cable. I actualy went and played with the cable a bit and now it seems to be in a position when it connects very fast. Also i do have the problem with wrong speed occasionaly ! I am on 100Mb line and occasionaly it will drop to 10Mb and i need to disable/enable the adapter. The cable is a few meters long. I will try another cable, maybe not the cheapest one like this time. I hope it works !
You're 'dropping pairs'. The conductors are probably stressed fractured from bending/pinching. It happens. More often than not, you just need to snip off a few cm / in. and re-terminate the patch cable.
Depending on your precise flavor of 'thriftiness' I have a suggestion for at least 2:
1. Getting some RJ45 crimp-ons and the tool is a worthwhile investment. (even the Harbor Freight and 'import' tools are typically at least "serviceable")
BTW, you can use either TIA-spec (for wiring the pairs); just make sure it's the same on both ends. (While I do not recommend purposely messing things up, as long as both ends are the same, the NIC and Router / Switch will 'negotiate' in most cases.)
Tip: use the snipped-off ends as a 1:1 guide for the new termination. (most are clear plastic)
2.Keep an eye out on eBay, etc. for 'Field Termination' or 'tool-less' RJ45 or '4p8c' and buy surplus ones on the cheap.
They're more bulky, but much tougher (rougher on RJ45 jacks too), but need no tools other than a Leatherman (multi-tool) or pocket knife/razor.
They're reusable too! -you get multiple tries w/o wasted crimp-ons.
Either direction, you'll have stuff on-hand for making and fixing Ethernet cables. THAT is really handy.
plus you can save a lot of copper and PVC making its way into the trash in refurbishing old cables.
Sidenote: IIRC US retail chain hardware stores Lowe's and Home Depot aren't bad on pre-made cable pricing.
(Figured I'd add, since depending on living circumstances, this might be an option)