After starting bitmonerod.exe it synchronizes with the network for some time till it tells me that it is synchronized and I can start up simplewallet.exe
You can try deleting/moving your binary wallet file (default name wallet.bin) and just keep your keys file (wallet.bin.keys), and then let simplewallet rebuild the binary file. If you're moving a wallet file from 32-bit to 64-bit this can definitely be an issue, also moving from *nix to windows I think.
make some backups btw.
Thx, I already did. Anyway my problem still persists, any ideas how to fix it?

My guess is that it is still finding a bin file somewhere. Post the log file again from simplewallet (redacting private stuff is fine, only the messages are important).
Thats the latest one (I cut a lot of lines out where it only processes blocks -> [...]:
2014-Aug-31 21:11:28.188406 bitmonero wallet v0.8.8.2(0.1-g1b8a68f)
2014-Aug-31 21:11:29.567485 Loaded wallet keys file, with public address: XXXXXXxXwmDs3R6rGkRHFJmjtk78KH87LsJSanmnxDF1xkyxeH3MeJZhZNdzNNF4DgYV8aGZoFFqNSfqVmhuUHhGyvvxgK
2014-Aug-31 21:11:29.597487 Opened wallet: XXXXXXxXwmDs3R6rGkRHFJmjtk78KH87LsJSanmnxDF1xkyxeH3MeJZhZNdzNNF4DgYV8aGZoFFqNSfqVmhuUHhGyvvxgK
2014-Aug-31 21:11:29.612488 Starting refresh...
2014-Aug-31 21:11:29.657490 Block is already in blockchain: e7e865e736fad684a7d7f6cd5bef581bfe1050d6a533622c2431ec8e0d7f106e
2014-Aug-31 21:11:29.660491 Processed block: <946ec45ee7c878c63a7c8e8d4fff28fc7585d0ba70a6a06cca8a9fad9c0a937d>, height 197737, 0(0/0)ms
2014-Aug-31 21:11:29.736495 Processed block: , height 197738, 62(0/62)ms
[...]
2014-Aug-31 21:11:30.868560 Refresh done, blocks received: 110, balance: XXX, unlocked: XXX
2014-Aug-31 21:11:30.870560 Refresh done, blocks received: 110
2014-Aug-31 21:11:30.871560 balance: XXX, unlocked balance: XXX
2014-Aug-31 21:11:30.874560 **********************************************************************
Use "help" command to see the list of available commands.
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